As knowledge continued to grow through travel and contact of Europeans with the New World, confusion over plant names and identities in the 13th-16th centuries foreshadowed what would become a growing problem in practical medicinal botany, the main precursor of the science of botany and botanical taxonomy (Sumner, 2000). There was need for a universal efficient system of plant naming as part of a classification system or an orderly arrangement of plants into groups on the basis of their medicinal similarities and shared characteristics of form and structure (Sumner, 2000). Standard ways of describing plants on the basis of characters or characteristics that can often be traced to ancient associations of plant forms and structures with parts of the human body are known to have become the actual name of the plant. The forms and structures as they develop from the immature to mature plant came to be referred to as plant morphology. Such forms and structures have also been referred to as the morphological characters of plants. In other words, the standard ways of characterizing the forms and structures became the physical characters; and often a series of some of the key characters used for identification often became the name. Such a name could be written as a sentence in Latin. A short hand system to simplify these long complicated plant names was developed in 1753 by the Swedish botanist Carl von Linné (1707-1778), better known as Carl Linnaeus. This was a system of shortened two worded names often describing the plant in Latin. Since it often uses only two words to name a plant species, this system is called binomial nomenclature. These two worded names could be placed in a classification system of different levels. Each level is named. The level higher than species (corresponding to the genus) is named by the first word of the two worded name. Prior to Linnaeus, Joseph Pitton Tournefort (~1700) was one of the first to group plants by genera (plural for genus). Next higher levels also have single worded names corresponding to what are now called subtribes, tribes, subfamilies, families, orders, classes, divisions or phyla, and so on. This system of named levels is called a ranked hierarchical classification system, also considered a contribution of Carl Linnaeus and often referred to as a Linnaean hierarchy from species to kingdom. Of course, Linnaeus was also a physician. In his day, to become a physician, one was compelled to become at least somewhat of a botanist. Just a few years before his taxonomic work (called Species Plantarum), he had published Materia Medica (1749), a reference book on medicinal plants for physicians. There were attempts of an earlier period to group plants according to medical properties. Although medicinal properties of plants were important to Linnaeus, there was a trend during his time and somewhat earlier to emphasize the overall similarity of certain morphological characters of plants as the main information used to group them in an orderly arrangement within a classification system. See history of scientific names and hierarchical classification now based on genealogy.

Today, scientific names (also called formal or taxonomic names) are (ideally) universal symbols (accepted internationally) in Latin and/or Greek for groups of living (or fossil) organisms that should (ideally) correspond to particular lineages. The rules for formally naming plants, including "algae" and fungi or any other type of organism traditionally treated as plants, are based on rules and recommendations of the International Code of Botanical Nomenclature or ICBN. There is a somewhat different code for cultivated plants. These are rules that help to ensure only one correct scientific name, the earliest published name, for a particular well circumscribed group of organisms. The principle of priority states that the earliest published names always have priority over other names except in certain specified cases, especially those cases involving revisions of groups, bearing older names, that are not well circumscribed (e.g., artificial groups that do not include true lineages). More modern approaches stress the need of applying formal names (whenever possible) only to well defined lineages. Scientific names are always composed of one or more Latin or 'Latinized' words. A legitimate scientific (taxonomic) name representing some group that is less inclusive than a kingdom and more inclusive than a genus should be based on a taxonomic name usually of some genus. Although the names, themselves, are much shorter than the old polynomials used prior to Linnaeus, in order to validly publish a new scientific name, this name must be accompanied by an often brief Latin diagnosis, which is one or more sentences in Latin describing the diagnostic (distinguishing) features useful for the identification or the circumscription of the plant or group of organisms so named. A name published with a Latin diagnosis has priority over a prior name published without such a diagnosis. Since the species is considered the fundamental taxonomic unit or category (the most basic one or the lowest-ranking normally used one), an attempt will be made to define this group first. On the basis of this definition, other more or less inclusive groups are then defined. Some rules for the names of species and other groups are discussed. However, this is done only after the reader is given a introductory explanation of the species as the most basic unit of classification.

A species can be for practical purposes defined as a group of organisms that is given a two worded name called a binomial by a competent biologist and that can be distinguished from other species. It can be very difficult to more clearly define a species, especially for plants that can reproduct both sexually and asexually (without sex) or any organisms that can only reproduct asexually. In order to be more precise, a species must unfortunately be defined in several ways, requiring different species concepts depending on the type of organisms considered. One of the most common of these concepts is that a species is a distinct lineage that, in sexually reproducing organisms, comprises a group of generally very similar looking, interbreeding populations that are (one way or another and more or less) reproductively isolated from other such groups. According to Ernst Mayr, biological species are "groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups." A population is then a group of individual organisms of the same species usually found in a specific geographical area that are typically capable of interbreeding. The minimum requirement for biological species is that they must be populations of individual organisms typically capable of potentially interbreeding and producing viable, fertile offspring. Although they may all look more or less alike, this is not enough to qualify as a member of the same biological species. They must all (with the obvious exception of sterile members) be potentially capable of breeding with each other (= interbreeding) to produce another generation of similar creatures. On the other hand, individuals of opposite sex from two populations belonging to different biological species are considered reproductively isolated from one another, because even though they may live in close contact or not, if they are brought together and attempt to breed, they cannot produce fertile offspring. In other cases, a species may not normally breed with other species or such breeding resulting in fertile organisms may be infrequent enough not to blur the species boundries.

The definition of species (singular or plural) can be first attempted according to the biological species concept, which can apply only to sexual organisms that undergo descent by sexual reproduction. Although a species is usually always considered a distinct lineage, other criteria, referred to as the cladistic or evolutionary species concept, ecological species concept, phenetic species concept, recognition species concept, etc., can be applied to asexual organisms (with only descent by asexual reproduction) or those sexual organisms that are distinct enough to be considered separate species but that do not fit the biological species concept. In other words, a species may or may not correspond to the biological species concept. If it does not correspond to a biological species, its distinction as a species can be based on various other definitions. For the scientific name of a species, see species name.

From the perspective of modern ecology (the study of the interactive relationships between living organisms and the environment), a community is typically the set of all the populations of different (often reproductively isolated) species that inhabit a particular geographic area. Each form of life comprising a community can be placed within a particular species. A community of organisms together with the abiotic (non-living) environment with which the community interacts is called an ecosystem (e.g., a particular type of forest, grassland, desert, coral reef, etc.). Therefore, an ecosystem comprises a community [all the living things (populations of species) in a particular area] together with all the nonliving (abiotic) components of the environment (e.g., atmospheric gases, light, soil, and water) with which the community interacts; and the biosphere comprises all the ecosystems of the planet.

The preoccupation of naturalists [today considered taxonomic biologist (or those that study ecology)] in the late eighteenth and early nineteenth centuries was the classification of the huge diversity of living organisms into groups called 'taxa.' The species defined to include members capable of interbreeding became the basic unit of classification. However, in cases where it was difficult or impossible to demonstrate interbreeding, the definition of a species was based entirely on similarity of morphology. It was soon discovered that some of the different species groups (although not usually capable of interbreeding with each other) were so similar that they could be placed into more inclusive (broader) 'taxon,' such as the 'genus,' which became a member of a 'family,' included as a member of an 'order,' included as a member of a 'class,' included as a member of a 'phylum' or 'division,' and finally included as a member of a 'kingdom.'

In land plants, scientific names can apply to named groups, including one kingdom (composed of divisions), divisions (each composed of classes), classes (each composed of subclasses or orders), orders (each composed of suborders or families), families (each composed of subfamilies, tribes, subtribes, or genera), genera (each composed of subgenera, sections, series, or species), and species (each composed subspecies, varieties, or forms, including populations often without names). This arrangement of names can be said to correspond to what is called a hierarchical structure of levels (similar in some ways to the older systematic arrangement of organisms attributed to Carl Linnaeus). Levels (at least the principal ones, including a kingdom, divisions, classes, orders, families, genera, and species) are said to be hierarchical, because each one includes all the other ones beneath or (as represented here) following it. Traditionally these levels have been referred to as ranks. Any individual plant can be said to belong to one and only one named kingdom, division, class, order, family, genus, and species. Since populations of the same species are not necessarily reproductively isolated from each other, an individual organism can also be said to belong to at least one or possibly more populations. It can sometimes be said to belong to one and only one named subclass, suborder, subfamily, tribe, subtribe, subgenus, section, series, subspecies, variety, or form, depending on whether these levels are defined. See example of the different ranks (based on lineages) for the medicinal genus Artemisia up to the level of order.

The species [including one or more populations (sometimes also including designated subspecific groups (= infraspecies), such as named subspecies, varieties, forma or races)] is considered the fundamental taxonomic unit or category that is below the level of the genus. The species name is represented by two words that are italicized or underlined (e.g., the species name for corn: Zea mays), sometimes followed by the author(s) of the name. Note that the first letter of the first word of the species name is capitalized, while this is usually not done for the second word. Some older species scientific names can be found that capitalize the first letter of both words (especially when the second word is derived from a proper name), but this is usually never done today. The scientific name of a species is called a binomial or binominal, since it has two parts, a capitalized generic name (same name as the genus), followed by an uncapitalized species epithet. The binomial for the species name is always composed of two Latin or 'Latinized' words. Although the rules for the endings of each of these words and other issues are not treated here, it might be worth mentioning that the two worded species name is treated as a Latin singular noun. This is also the case for names at or below the rank of genus. Only those names above the rank of genus are treated as Latin plural nouns. See a few further comments on the history of what is called binomial nomenclature (the formal method of naming species). Sometimes the author(s) of the binomial are optionally included after the species epithet [e.g., the full name (including authorship) for Zea mays is Zea mays L.]. This author(s) designation, often only abbreviated, is capitalized but never italicized or underlined.

When species are intentionally not completely identified, the abbreviation 'sp.' in the singular or 'spp.' in the plural, following the generic name, is used without reference to any species epithet. Only the generic name with the first letter capitalized is italicized. For example, in the particular genus for pines, Pinus sp. or Pinus spp. applies to a single unidentified species or several but not all species, respectively. Therefore, the abbreviation 'sp.' applies to individuals belonging to a particular genus but the exact species remains unidentified, while 'spp.' applies to at least some but not all species within this genus. If it applies to all species within a genus, the generic name by itself is used.

Species may include two or more infraspecific ranks (below the rank of species) referred to as subspecies or varieties. A subspecies is generally understood as a infraspecfic rank with defining characteristics within a given geographical range (or ecological niche) that differ from other subspecies within other geographical ranges (or niches), while a variety is generally understood as a infraspecfic rank with characteristics without clearly defined geographical or ecological distribution that differ in only minor ways from those characteristics usual for the species. In naming subspecies or variety (examples of subspecific groups), the two worded species name comes first and, next, the so-called epithet for the subspecies or variety follows the abbreviation, subsp. (or ssp.) or var., with the author(s) of only the subspecies or variety epithet sometimes (optionally) included last. Of course, the abbreviation, ssp., corresponds to subspecies, while the abbreviation, var., represents variety. Again (as above), only the first letter of the first word of the italicized or underlined species name is capitalized. The single worded subspecies or variety epithet is italicized or underlined, but its first letter is not capitalized. The epithets, no matter what rank, are usually never capitalized. The only words that are italicized or underlined apply to the two worded species name and the single worded subspecies or variety epithet. Therefore, for the species and lower ranking groups, only the generic name and one or more epithets are italicized or underlined. The rest of the words in the scientific name are not italicized or underlined and apply to an abbreviation, subsp. (ssp.) or var., and (if included) the often abbreviated author(s) of the subspecies or variety epithet. Since there can be three italicized or underlined Latin or 'Latinized' words, a three worded subspecies or variety name is called a trinomial (meaning three names). The author(s) of the two worded species name can be optionally included in addition to the author(s) of the subspecies or variety epithet. When this is done, the author(s) of the species directly follow its two worded name and the author(s) of the subspecies or variety directly follow its single worded epithet. Although subspecies and variety are sometimes used interchangeably, subspecies is technically ranked at a higher level than variety, which means that a subspecies can include two or more varieties. This can result in a name for a variety being composed of four italicized or underlined words (a quadrinomial, meaning four names). In this case, author(s) can be included directly after the two worded species name, other author(s) directly after the subspecies epithet, and still other author(s) directly after the varietal epithet. Often only the author(s) for the varietal epithet are included. Of course, the abbreviation ssp. comes directly before the subspecies epithet and var. directly before the epithet for variety. See example for some subspecies and variety names of the medicinal species Achillea millefolium.

A genus is usually considered a group of very closely related species, each of which can be composed of more than one subspecies or variety. A genus name is the first word of any of its species names, including infraspecific names below the rank of species for subspecific groups (i.e., subspecies, variety, or forma). In other words, all member species of a genus are distinguished by the second word of their scientific name and have the same first word called the genus name. Subspecies or varieties of a given species of a genus have the same two worded (italicized) species name and are distinguished by the third or even fourth (italicized) word in their names. Therefore, the name of a genus is always a single, italicized or underlined word with its first letter capitalized (e.g., the genus name for corn: Zea). The often abbreviated author(s) of the genus name are optionally placed at the end of the name [e.g., the full name (including authorship) for the genus Zea is Zea L.]. Again, some of the older names for genera (plural for genus) were often derived from or identical to old Greek names for groups of (ideally) closely related species. This is consistent with ICBN rule of priority of the earliest names. Only after a genus name is at least completely spelled out [with or without its author(s)], so that it cannot be confused with any other genus name, can a genus name be abbreviated by the capitalized first letter followed by a period. Thus, the species for corn can be abbreviated as Z. mays, only after Zea has been spelled out in full.

When a subgroup called a subgenus, section, or series of a genus is sometimes defined, the name of each subgroup can have various endings. Often (but not necessarily) a subgenus can be named by a capitalized species epithet, comprising all the species that are ideally most closely related to the one bearing the species epithet; and only one of the subgenera (plural for subgenus) bears the same name as the entire genus. For example, the two subgenera for the genus Equisetum are Equisetum subgenus Equisetum and Equisetum subgenus Hippochaete. Note that the subgenera names (Equisetum and Hippochaete) are also italicized. In this example, the subgenus Hippochaete is not a capitalized species epithet of any of its species, but the subgenus Equisetum has the same name as the entire genus. The medicinal species with scientific name Equisetum arvense is commonly referred to (in Spanish) as Cola de caballo. It belongs (along with certain other species commonly designated in English as "Horsetails") to Equisetum subgenus Equisetum. The medicinal species with scientific name Equisetum hyemale is commonly referred to (in Spanish) as Canutillo del llano. It belongs (along with certain other species commonly designated in English as "Scouring rushes") to Equisetum subgenus Hippochaete. See also short mention of two subgenera for Wormwood and Mugwort. Examples of published names for sections or series (when defined) will not be given here, but the reader should be aware that sections are subgroups (made up of species) placed within subgenera; and series are subgroups (also made up of species) placed within sections. Of course, authors of all these names can again be optionally included after the italicized part.

A family can be thought of as a group of closely related genera (plural for genus). The family name is a single word ending in the suffix -aceae (e.g., Poaceae). The Grass family is called Poaceae; the Sunflower family is called Asteraceae; and so on. For example, the genus Zea (for corn), including one of its species Zea mays, is in the family Poaceae, while the genus Achillea (for yarrow), including one of its species Achillea millefolium, is in the family Asteraceae. The often abbreviated author(s) of the family name are optionally placed at the end of the name [e.g., the full name (including authorship) for the family Poaceae is Poaceae Barnhart or Poaceae (R.Br.) Barnh.]. Although there is a trend today to use the suffix -aceae for all family names, the reader should be aware of eight alternative family names that do not end in this way. These include Compositae (= Asteraceae), Cruciferae (= Brassicaceae), Gramineae (= Poaceae), Guttiferae (= Clusiaceae + Hypericaceae), Labiatae (= Lamiaceae), Leguminosae (= Fabaceae), Palmae (= Arecaceae), and Umbelliferae (= Apiaceae). Most of these are old family names that represent groups of plants that may have been recognized since ancient times. These alternative names are often used in older but sometimes even more modern works on plant taxonomy. Although the scientific names for species (including epithets for subspecies, varieties, or forms) and genera (including epithets for subgenera, sections, and series) should always be in italics or underlined, this practice is optional for the family names (including those of subfamilies, tribes, and subtribes), as well as order, class, and division names. The single word names for these more inclusive taxonomic units (taxa) are usually not underlined or italicized. However, as in the family Poaceae (R.Br.) Barnh., the often abbreviated author(s) of the single word name of the more inclusive group can optionally be placed at the end of the name.
The practice in recent editions of the ICBN Code is to place all scientific names regardless of rank in italic type. This author still adheres to the old standard of italicizing scientific names at or below the rank of genus, but only optionally places names above the rank of genus in bold type, especially when the formal names represent well supported lineages (e.g., many current names for orders of flowering plants).

A family can be subdivided into subfamilies and tribes. If subfamilies are defined, they can sometimes be subdivided into supertribes or tribes. By convention, the subfamily name ends in the suffix -oideae, while the supertribe name ends in the suffix -odae and the tribe name ends in the suffix -eae (subtribe names end in the suffix -inae). Families can be grouped into superorders (with suffix -anae) or orders (with suffix -ales) and orders into classes (with suffix -opsida or in "algae", -ophyceae). Orders comprising families can also be subdivided into suborders (with suffix -ineae) and classes comprising orders can be subdivided into subclasses (with suffix -idae). A division (= phylum) or a subdivision (if defined) is a group of classes. A division name ends in the suffix -phyta. A subdivision (below a division) ends in the suffix -phytina. A kingdom name can have various endings. Again, a legitimate scientific (taxonomic) name representing some group that is less inclusive than a kingdom and more inclusive than a genus is usually based on a taxonomic name (usually some genus name); and often abbreviated author(s) of these names are optionally placed at the end of the names.

However, formal but descriptive names (not based on some taxonomic name) with the proper suffices can also be used for certain ranks. For example, in the classification of Chase & Reveal (2009), the proposed class name Equisetopsida C. Agardh sensu Chase & Reveal for entire lineage of land plants (= embryophytes) is potentially confusing, because the name Equisetopsida C. Agardh has been widely used in other classification systems for a much less inclusive class name that includes the genus Equisetum L. (horsetails). Although not based on any validly published genus or other taxonomic name, Pirani & Prado (2012) has proposed a new, more descriptive class name Embryopsida Engler ex Pirani & J. Prado, 2012 for land plants based on the rule that the principle of priority does not apply above the family rank and the provision for descriptive names [Art. 16.1(b)] of both the Vienna Code and Melbourne Code. Kingdom or domain (superkingdom) names are not necessarily based on a taxonomic name. Presently, the kingdom formally but descriptively named Chlorobionta Jeffrey 1982, emend. Bremer 1985, emend. Lewis and McCourt 2004 = Viridiplantae Cavalier-Smith, 1981 includes only a large subset of the organisms traditionally considered "plants". This kingdom comprises a large lineage that can also be referred to informally as green plants (= viridophytes). Although names below the rank of kingdom and above the rank of order are often based on some taxonomic name, alternative formal and descriptive names can also be proposed and adopted. For example, the formal division name Streptophyta Jeffrey 1967, sensu Leliaert et al. 2012 for the lineage that includes "streptophyte green algae" plus land plants is not based on some (lower rank) taxonomic name.

In the eighteenth century, Linnaeus popularized the idea (Lemery, 1675) that nature can be divided into three kingdoms, mineral, vegetable (plant) and animal. N. J. de Necker may be the first recorded to propose the separate status of fungi as early as 1783. Although the rules for naming both plants (e.g., mosses and marigolds) and fungi (e.g., molds and mushrooms) are still dictated by the ICBN Code, it was decided by R. Villemet (1784) that fungi are unique enough to be placed in their own kingdom separate from plants. At that time period, only three kingdoms of life were sometimes recognized, corresponding to plants, fungi, and animals. Even though a three kingdom system had already been proposed, the older two kingdom system, including only plants and animals, considering fungi as unusual types of plants, was still widely used well into the early part of the 20th century. Actually, the organisms of the gigantic and diverse kingdom Fungi of today were all classified [according to Moore (2013)] as "plants" right up to the middle of the twentieth century. This is because a separate kingdom for fungi was not generally accepted until the proposals of Whittaker (1959) for the five kingdom system, dividing all life into the kingdoms of animals, plants, fungi, "protists" and "bacteria". In the two kingdom system of classification of the early 20th century, the plant kingdom was roughly defined to include (1) "Thallophyta" ["algae", including "chromistan algae," as well as what was once called blue-green algae (= cyanobacteria), "bacteria" (= "Monera"), fungi, "lichens" and "fungus-like organisms")], (2) Bryophyta s.l. (= liverworts, mosses, and hornworts), (3) "Pteridophyta" [ferns and "fern allies" (often including horsetails and lycophytes)], and (4) Spermatophyta (seed plants, including flowering plants). Bryophytes have until just recently (2018) been considered paraphyletic, but some DNA analyses now provide evidence that they might (?) form a monophyletic group sister to vascular plants [see Puttick et al. (2018)]. Biology still includes the two major divisions of botany and zoology. At the time that the rules for naming organisms were codified in the late 19th century, there were only two Codes: one for animals and the other for what were called "plants".

Irrespective of whether a two or three kingdom system of life, the animal kingdom often referred to as Metazoa Haeckel has remained over the years of the 20th century relatively stable (with only a few variations in the names of certain major groups). It has comprised for a long time at least the major phyla of multicellular organisms, such as Porifera (sponges), "Coelenterata" (sea anemones, jelly fish, comb jellies, etc.), Platyhelminthes (flatworms), Nemathelminthes (roundworms), Mollusca (molluscs), Annelida (segmented worms), Arthropoda (insects, spiders, etc.), Echinodermata (star fish, etc.), and Chordata (sea squirts, lancelets, vertebrates, etc.). However, sometimes (prior to the 20th century), the "animal-like group" often called the "Protozoa" (Owen, 1858) that consists mostly of single cells (Von Siebold, 1845) was (at least traditionally) considered part of the animal kingdom. Although Owen is often considered the first to propose the name "Protozoa," Goldfuss (1820) introduced this name first in 1817. This was initially a newer name for microscopic "animal-like" organisms once referred to as "Infusoria" (a name that was later applied just to the ciliates). Haeckel (1866) defined "Protists" or "Protista" (currently used mostly as vernacular name for a polyphyletic grade) as consisting of only "unicellular (single-celled) organisms," many of which are now known to group in various unrelated kingdoms. Haeckel's proposed "Protista" originally merged the large (mostly) unicellular kingdom later called "Monera" (= "bacteria" - "prokaryote organisms" with absence of a well defined nucleus) together with several unrelated (mostly) unicellular (microbial) groups later recognized as eukaryotes (organisms with a well defined nucleus). Haeckel (probably the first to propose the term 'phylogeny' for the evolutionary history, including genealogy, of organisms) defined his tree of life as comprising three major branches, which he called the kingdoms Animalia, Plantae, and "Protista." Even though he grouped all heterotrophic "bacteria" along with, for example, "amoebae" and sponges in "Protista" and cyanobacteria (blue-green algae) in "Plantae", he thought that his three kingdoms were actual lineages. Later he moved "amoebae" and sponges to "Animalia."
Before "Protista" for single celled organisms was proposed by Haeckel (1866), living organisms were more or less still generally considered to comprise only the two kingdoms of animals and vegetables, even though Necker and Villemet had already proposed a distinct kingdom for fungi or Goldfuss and Owen had already placed unicellular organisms (e.g., "bacteria" and "amoebae") in a distinct kingdom "Protozoa." Apparently, the distinction between "bacteria" and "unicellular eukaryotes" had not yet been recognized. However, eventually Cohn (1875) proposed the name "Schizophyta" for all "bacteria" as distinct from all eukaryotes. This foreshadowed the still widely employed division of all living organisms as "prokaryotes" versus eukaryotes. Another modern but obviously artificial division of all life is "macroorganisms" versus "microorganisms" ["animals + land plants" versus all "left-over organisms" (including viruses) that are neither land plants nor animals). Today, the name "Protista" (or "protists") is often reserved for unicellular or multicellular "algae" plus mainly unicellular "protozoa".

Although certain so-called "protozoan" organisms like choanoflagellates and ichthyosporeans (= mesomycetozoans, corallochytrids, and also perhaps eccrinids) are now considered to have a closer relationship to animals than any other major group (see animal side of neozoan tree), the "Protozoa" (literally, "first animals") are today considered an artificial kingdom of mostly unrelated, single-celled organisms distinct from all animals, as well as "bacteria", fungi, and plants. Nevertheless, at least as far as the rules for formal names are concerned, most "Protozoa" and animals are still considered the two zoological (animal) kingdoms. Consequently, the names of both "animal-like protozoans" and the animals, themselves, are subject to the International Code of Zoological Nomenclature or ICZN. This is still the case, even though the members of "Protozoa" are now placed in various (often unrelated) phyla currently considered separate from multicellular (many-celled) animals. As a collection of generally unrelated organisms, the "animal-like protozoans" have retained many characteristics that were likely present in some of the first eukaryotes (literally, the entire group of organisms that possess a 'true nucleus'). Most are ancestrally unicellular (single-celled) or plasmodial [with many nuclei (plural for nucleus) not partitioned into individual cells], often motile (able to move from place to place), heterotophic (non-food-producing and depending on other organisms for food), phagotrophic (often phagocytic), sometimes osmotrophic, sometimes forming colonies of loosely interdependent single cells, but predominantly non-filamentous (usually never elongated filaments several cells long and one or a few cells wide), lacking protein called collagen, and cell walls usually absent (but if present, not composed of any chitin). In contrast, animals are considered heterotrophic, phagotrophic or sometimes osmotrophic, always multicellular (many-celled) eukaryotes with intercellular (between cell) connections called gap junctions, lacking cell walls or spores, possessing fibrous proteins (mostly collagens) that forms a matrix of connective tissue between the cells, and ancestrally (?) with hallow spherical blastula stage larvae [fertilized eggs or zygotes of some sponges developing into loosely multicellular larvae that at least resemble hallow spherical collections of cells called blastulae, but (unlike other animals) each cell facing the outside bearing a single whip-tail-like flagellum for propulsion or motility and dispersal of larvae].

The lineage named Metazoa Haeckel is presently sometimes defined as the more inclusive group of animals, comprised of Porifera Grant (= Parazoa Sollas), Trichoplax von Schultze (= Placozoa Grell), Mesozoa van Beneden, and Animalia Linnaeus (= Eumetazoa Butschli, containing Myxozoa Grasse that is secondarily reduced to small number of cells). Some of the major diagnostic characters have already been listed above for organisms that most people would consider animals. The Eumetazoa possess heterotrophic nutrition that often involves phagotrophy [= ingestion; e.g., eating by the swallowing (whole or in pieces) of organisms (or their dead remains called detritus)] with secretion of digestive enzymes and sometimes osmotrophy (~= absorption) through a digestive tract. The activities of the many cells (organized as true tissues, often involving tissue systems, organs, or organ systems) of Eumetazoa are controlled and coordinated via elaborate signal transduction pathways (cascades of sequential biochemical events, often culminating with the expression of genes) that can be thought of as responses initiated often by plasma membrane (cell-surface) receptors proteins that selectively bind to specific ligands (other substances that act as external signal molecules). In other words, as a consequence of the binding of a ligand by a cell membrane receptor protein, the transfer of a signal through a series of intermediate molecules (collectively called a signal transduction pathway) can take place until final regulatory molecules, such as protein transcription factors that regulate gene expression, are modified in response to the signal. Although signal transduction pathways can be found in almost all organisms, especially those with multicellularity, the more elaborate pathways are more common in animals. The consideration of these often more elaborate signal transduction pathways found in Eumetazoa are important to the understanding of natural medicinal resources, because the characterization of such events is, for example, basic to the understanding of how bioactive, medicinal chemicals, or toxins (often acting as ligands) affect the living processes of the cells of these organisms; and such substances can play a critical role in ecological relationships between animal primary consumers and plant primary producers. Generally, many of these substances (potentially produced as allelochemicals by almost any type of organism) are now viewed as important in ecology in the establishment and maintenance of interspecific (between species) relationships. Plant versus animal interaction may be a major reason why certain plants possess chemicals with properties of interest to medicine. Examples of many of these organic (carbon containing) chemicals function as defensive compounds synthesized in plants through the aid of the food producting process called photosynthesis. Many of these substances that are often relatively small but more complex than such compounds as carbon dioxide (CO₂) can be considered animal repellents (Fraenkel, 1959).

What type of organisms should be considered members of the Plant Kingdom?

Classification systems of plants that start at the rank of kingdom may differ widely depending on what groups of organisms are considered 'plants.' This can result in differences in names, especially the parts of the names called suffixes, due to different ranges of organisms included in the ranks from one classification to the next. This problem is more directly discussed below. However, in this section on the Plant Kingdom, there is an emphasis on various ways of defining what are commonly referred to as 'plants.' These organisms are often broadly distinguished from other organisms by their ability to carry out the sun-light driven, food producing process called photosynthesis, but not all organisms considered 'plants' historically or even today have this ability; and some organisms that can carry out this process are today not considered plants even though they were considered so in the past. Because of these and other issues, some authorities that devoit most of their attention to embryophyte land plants even distinguish what they call 'plant science' from botany. These issues are addressed in this section by first introducing a few definitions that will hopefully provide the reader with a basic understanding of what is meant by photosynthesis. Some of the major ways of defining what are called 'plants' are then summarized by the topics that follow on the oxygenic photosynthetic organisms, photoautotrophic eukaryotes, first eukaryotic photoautotrophs [also called primary photosynthetic eukaryotes (PPEs)?], viridophytes, streptophytes, and embryophytes.

What is photosynthesis?

A detailed discription (e.g., all the specific chemical reactions) of the very complex process of photosynthesis is not covered here. However, inorder for the reader to better understand the short definitions of this process covered below, a brief discussion of what chemists call oxidation and reduction can be helpful, because photosynthesis is based on a fairly complex series of light driven oxidation and reduction chemical reactions call redox reactions.
If an organic chemical compound is characterized as usually a more complex substance that always at least contains both carbon (C) and hydrogen (H) atoms [with or without other atoms common to life, such as oxygen (O) atoms, nitrogen (N), sulfur (S), phosphorus (P) atoms, and metals such as iron, magnesium, and zinc], than any element or simpler chemical compound that does not quite fit this characterization can usually be considered an inorganic chemical compound (= inorganic type substance or a mineral). Only the relatively simple carbon compounds, such as carbon monoxide (CO), carbon dioxide (CO₂), and carbon disulfide (CS₂), as well as the metal carbonates, bicarbonates, cyanides, thiocyanates, cyanates, and carbides, are considered inorganic compounds. Photosynthesis utilizes redox reactions driven by light energy to convert some simple inorganic chemical to a more complex organic chemical used as food.
Reduction is at least the gain of one or more electrons by a chemical substance, often accompanied by the gain of one or more protons (hydrogen ions) or the gain of one or more hydrogen atoms; it can also involve removal of oxygen chemically from a substance; and it is accompanied by a gain in energy. Any substance that has this happen to it is said to be reduced. The adding of electrons to a substance is called reduction, because the negatively charged electrons added reduce the amount of positive charge that any reduced substance contains. Any chemical reaction that causes this to happen is called a reduction reaction.
Oxidation is at least the loss of one or more electrons from a chemical substance, often accompanied by the transfer of one or more protons (loss of hydrogen ions) or the loss of one or more hydrogen atoms; it can also involve addition of oxygen chemically to an atom or molecule; and it is accompanied by a loss in energy. Any substance that has this happen to it is said to be oxidized. Any chemical reaction that causes this to happen is called an oxidation reaction.
Oxidation and reduction reactions are together often represented as a single reaction, because oxidation cannot occur without reduction or vice versa and an electron transfer requires both a donor and an acceptor. This single reaction, comprising an oxidation and reduction reaction, is called an oxidation-reduction or redox reaction. The substance that accepts one or more electrons, hydrogen ions (protons), or hydrogen atoms (or loses oxygen atoms) and thereby becomes reduced is called the oxidant or oxidizing agent, while the substance that donates one or more electrons, hydrogen ions (protons), or hydrogen atoms (or gains oxygen atoms) and thereby becomes oxidized is called the reductant or reducing agent. The substance that is oxidized (the reducing agent) loses electrons and energy, while the substance reduced (the oxidizing agent) gains electrons and energy.
Chemical compounds that can be potentially oxidized and utilized as a source of electrons and energy can be said to be reduced chemicals. Fully oxidized chemicals without any available electons cannot be used as a source of electrons and energy. The inorganic chemical compound CO₂ utilized as a carbon source in photosynthesis cannot also be used as a source of electrons, because CO₂ is a source of carbon that is completely stripped of electrons (fully oxidized). Therefore, some other inorganic compound capable of being oxidized most be utilized as a source of electrons to help build energy rich food compounds.

The process of photosynthesis can be strictly defined as conversion of light energy usually from the Sun into chemical energy by using carbon dioxide (CO₂) as the sole inorganic carbon source for organic food production. Any organism that produces food (e.g., sugar) by using (1) light as its principal energy source, (2) some inorganic compound [e.g., ferrous iron (Fe++), hydrogen sulfide (H₂S), hydrogen gas (H₂), water (H₂O)] as its electron source, and (3) CO₂ as its sole carbon source can be considered a photosynthetic organism, which is also called a photoautotroph [= photolithoautotroph, where 'litho' (literally pertaining to rocks) applies to an inorganic source of electrons, such as H₂O or even some substance (e.g., Fe++ called ferrous iron) contained in rocks].
Any organism that cannot use CO₂ as the inorganic carbon source to produce (its own) organic food is called a heterotroph (essentially not a food producer but a food consumer), while any organism (whether photosynthetic or chemosynthetic) that uses CO₂ as the carbon source for food production is called an autotroph. Heterotrophs are 'nourished by others' and autotrophs are 'self-nourishers.'
There are also chemotrophs [utiliizing chemical reactions (redox reactions) as energy source], mixotrophs, organotrophs [utilizing organic compounds as electron (sources) donors], lithotrophs [utilizing inorganic compounds [e.g., H₂O, H₂, Sulfur (S)] as electon (sources) donors], and phototrophs [utilizing light as energy source].
Only photolithoautotrophs can be strictly considered photosynthetic organisms, because photosynthesis can be strictly defined as a process that utilizes the inorganic compound CO₂ as the sole carbon source, some other inorganic substance as the electron source, and light as the principal energy source in order to produce (synthesize) organic food compounds. The definition of photosynthesis is commonly broadened to include certain phototrophs that are not considered autotrophs. For example, see the definitions of photosynthesis provided by Robert E. Blankenship (2014). There is not yet a complete consensus (see below) among various specialist authorities on what phototrophs to include or exclude as photosynthetic organisms.

Examples of some of the various possible nutritional patterns

Chemotrophs use chemical (redox) reactions as an energy source. There exist in nature chemotrophs that can also be considered heterotrophs (chemoheterotrophs), autotrophs (chemoautotrophs), lithotrophs (chemolithotrophs), or organotrophs (chemoorganotrophs), but probably not pure (obligate) chemoorganoautotrophs [other than certain mixotrophs called chemomixotrophs (= facultative chemolithoautotroph) with mixed organic and inorganic electron and carbon sources]. Animals, fungi, some parasitic plants, and many prokaryotes are chemoorganoheterotrophs.
Chemolithoautotrophs are chemosynthetic organisms (prokaryotes) able to reduce CO₂ to produce more complex organic compounds by oxidizing certain (reduced) inorganic chemical compounds [e.g., ferrous iron (Fe++), hydrogen sulfide (H₂S), ammonium (NH₄+), methane (CH₄), hydrogen gas (H₂)] as an energy and electron source.
Mixotrophs are organisms that have the capability to be autotrophs and heterotrophs at the same time. For example, an organism that can live as a chemolithoautotroph capable of using the CO₂ and at the same time organic compounds as a source of carbon is considered a mixotroph.
Because (reduced) inorganic compounds can sometimes become in short supply in the environment, a rudimentary form of 'photosynthesis' could have originated from chemolithoautotrophs that were able to synthesize special light absorbing pigments [possibly Mg-tetrapyrroles eventually somewhat similar to (bacterio)chlorophyll and carotenoids]. This would inable these chemolitho-photo-mixotrophs to live as chemolithoautotrophs and at the same time have the capacity as phototrophs to utilize light as a supplementary energy source. There are presently no known living mixotrophs like this on Earth, but if they existed in the past, they could have served as a possible evolutionary link between chemolithoautotrophs and photolithoautotrophs (photosynthetic organisms). Any organism that uses light as the source of energy to produce the molecule ATP needed as the principal molecular (chemical) energy source inorder to carry out various cellular processes can be considered a phototroph. Some presently living phototrophs considered photolithoheterotrophs with (bacterio)chlorophyll are able to utilize light as supplementary energy and exploit simple organic compounds in the environment as a carbon source for making more complex organic compounds. Therefore, photolithoautotrophs could have (perhaps more likely) originated from heterotrophs. However, when used as a carbon source, even simple organic compounds can sometimes also become in short supply. The origin of photosynthetic organisms is still a big mystery to science (Xiong, 2007).
According to some microbiologists (scientists that study "microorganisms"), not all phototrophs are considered photosynthetic organisms that are capable of carrying out photosynthesis (when strictly defined as involving light as the principal energy source, some reduced inorganic chemical compound as a source of electrons, and CO₂ as the sole carbon source). For example, photoheterotrophs (e.g., purple non-sulfur bacteria, some green non-sulfur bacteria, and heliobacteria) that build (synthesize) various more complex organic chemical structures by utilizing light as an energy source, organic (or inorganic) chemical compounds as an electron source, and organic chemical compounds as the carbon source are not considered (at least by these microbiologists) as photosynthetic organisms. In contrast, some microbiologists or other scientists can commonly refer to the purple non-sulfur bacteria and other photoheterotrophs as capable of carrying out a rudimentary form of 'photosynthesis' by using light only to supplement their energy supply.

Robert E. Blankenship (2014) provides a more 'generous definition' of photosynthesis that even includes as photosynthetic those organisms that use light only to supplement their energy supply. To get his points acrossed, he at first introduces photosynthesis (literally 'synthesis with light') as 'a biological process whereby the Sun's energy is captured and stored by a series of events that convert the pure energy of light into the free energy needed to power life.' Since the capturing of energy is never 100% efficient and some of it becomes unusable as heat, free energy is that part of the energy actually captured and available to carry out life processes. In tern, this author first provides the following broad definition:
'Photosynthesis is a process in which light energy is captured and stored by an organism, and the stored energy is used to drive energy-requiring cellular processes.'
However, unlike certain other specialist authorities, he subsequently restricts his definition to mostly the more familiar chlorophyll or (bacterio)chlorophyll-based form of photosynthesis (the subject of his book), excluding the rhodopsin-type of photosynthesis of certain archaea and other prokaryotes, which is somewhat similar to the light-driven signaling process called vision. He also excludes any process in which 'light conveys information instead of energy.' Even though restricting his definition to mostly chlorophyll or (bacterio)chlorophyll-based forms of photosynthesis, he is liberal enough to include those organisms that are capable of deriving some of their cellular energy from light.
[Chlorophyll or (bacterio)chlorophyll is a light absorbing (Mg-tetrapyrrole or 'chlorophyll-type') pigment that operates in a light-driven electron transfer process (involving redox chemical reactions) to capture usable energy.]
Blankenship (2014) justifies the broader definition of photosynthesis by the following:
"We adopt this broad definition because our interest is primarily in understanding the energy storage process itself. Organisms that use photosynthesis only part of the time may still have important things to teach us about how the process works and therefore deserve our attention, even though a purist might not classify them as true photosynthetic organisms. We will also use both of the terms 'photosynthetic' and 'phototrophic' when describing organisms that can carry out photosynthesis. We will usually use photosynthetic to describe higher plants, algae, and cyanobacteria that derive most or all of their energy needs from light, and phototrophic to describe bacteria or archaea that can do photosynthesis but often derive much of their energy needs from other sources."
[The archaea are only briefly mentioned in this web page in discussions about microbial life and relatedness.]

Full-fledged photosynthesis would not have developed until organisms were able to use light as their sole energy source, some very common inorganic compound as their electron source, and inorganic CO₂ as their sole carbon source. If the process of photosynthesis takes place by utilizing light (as the principal energy source), absorbing carbon dioxide from the surroundings (as the sole source of carbon), and splitting water via light (as the source of electrons) to liberate oxygen (as a by-product) into the surroundings, it is called oxygenic photosynthesis.
Even though it is still a big mystery precisely how oxygenic photosynthesis originated from forms of photosynthesis that did not liberate oxygen called non-oxygenic or anoxygenic photosynthesis (like those mentioned above), there is some fossil and DNA evidence that anoxygenic photosynthesis may have preceded oxygenic photosynthesis by at least a billion years. Nevertheless, there is overwhelming supportive evidence that the rudimentary forms of anoxygenic photosynthesis originated prior to oxygenic photosynthesis (Xiong, 2007). However, it was not until the development of oxygenic photosynthesis that organism could more fully utilize light (as their principal energy source) and simple inorganic chemical compounds [H₂O (as their source of electons) and and CO₂ (as their source carbon)] to build (synthesize) the more complex organic chemical compounds (e.g., sugars) commonly referred to as food.
The overall process of oxygenic photosynthesis can be summarized by the following chemical equation of initial reactants and final products:
CO₂ (carbon dioxide) + H₂O (water) + light -->
(CH₂O)_n (some sugar or carbohydrate) + O₂ (oxygen).
In most presently living photosynthetic organisms, the inorganic compound water (H₂O), often plentiful but often difficult to oxidize (see below), is used as a source of electrons. This is accomplished in a special process involving photolysis (= the splitting of water with the help of light). This results in the stripping of electrons from water and the liberation of free oxygen (O₂) into the surroundings.
Photolysis of water can be summarized by the following chemical reaction:
H₂O + light --> ½O₂ + 2H+ (hydrogen ions or protons) + 2e- (electrons)
Oxygen is one of the most powerful oxidants (oxidizing agents) known; it acts as the terminal electron acceptor in the complex series of redox reactions (often referred to as an electron transport chain) involved in aerobic (oxygen-dependent) respiration.
Oxygenic photosynthesis uses light energy to remove electrons and associated hydrogen atoms from water with the consequent release of oxygen gas. In turn, the energetic (high energy) electrons are used to produce (in the process called the light reaction) the molecules NADPH₂ and ATP, providing a biochemically effective source of electrons ("reducing power") and free energy required in order to convert (in the process called the dark reaction) carbon dioxide into more complex organic molecules. Some bacteria that carry out anoxygenic photosynthesis do not generate O₂, because they obtain electrons from such substances as H₂S or organic compounds rather than from water.
The origin of oxygenic photosynthesis in cyanobacteria is arguably the most important chemical reaction on the planet, because it was through the generation of most of the oxygen in the atmosphere and the eventual shielding (around 500 million years ago) of the surface of the planet from lethal UV radiation by the formation of the ozone layer that oxygenic photosynthesis has made possible the origin of more effective, oxygen dependent respiration and in turn the development of more advanced forms of life.
Due to the relatively high 'pull' of electrons by oxygen compared to other elements besides fluorine, it is much harder to strip electrons from water to reduce the carbon of carbon dioxide and produce sugar and the by-product O₂. However, by utilizing light energy from the Sun, the plants do this all the time in the process called oxygenic photosynthesis. The general chemical equations for aerobic (oxygen dependent) respiration [(CH₂O)_n + O₂ --> CO₂ + H₂O] and oxygenic photosynthesis [CO₂ + H₂O + light --> (CH₂O)_n + O₂] are actually summaries of processes involving many redox reactions. Furthermore, the flow of sunlight through the ecosystem drives a cycle involving the redox reactions of oxygenic photosynthesis and the redox reactions of aerobic respiration. Through the interplay of oxygenic photosynthesis and aerobic respiration together with the various processes called chemosynthesis, nitrogen fixation, denitrofication, anoxygenic photosynthesis, non-oxygen-dependent respiration, fermentation, and decomposition, this flow of energy from the Sun also drives the cycling of mineral (inorganic) nutrients and leaves the ecosystem as thermal energy or heat. The mineral nutrient products of decomposition in the air, water, and soil are picked up by plants and used to produce organic compounds, these organic compounds (including food) and oxygen produced by most plants are used in the aerobic respiration of most organisms (including the plants) and the carbon dioxide and water produced by these respiratory processes is used by most plants to produce more organic compounds and oxygen.

What is a plant?

Some authorities may attempt to define plants broadly to include organisms that directly produce food by oxygenic photosynthesis (Bell and Hemsley, 2000). Of all the organisms that fit this category, there is only one specific group of "prokaryotes" (organisms without a well defined nucleus within their cells) called cyanobacteria and the rest are various specific groups eukaryotes (organisms with a well defined nucleus). As mentioned above, there are also certain phototrophs (photoautotrophs and photoheterotrophs) that can carry out a type of non-oxygenic or anoxygenic photosynthesis that does not generate oxygen as a by-product. These are also bacteria, but they are not considered plants, because even though they are generally considered phototrophs, they do not generate oxygen. This may be considered a somewhat arbitrary way of deciding what is a plant versus what is not a plant. However, the few recent books dealing with the plant kingdom as broadly defined to include cyanobacteria do not include the "non-oxygenic photosynthetic bacteria." The oxygenic-photosynthetic cyanobacteria are the only "prokaryotes" that have traditionally been considered "algae" (the so-called blue green algae). Although the ancestry of some of the non-oxygenic photosynthetic bacteria may predate oxygenic photosynthesis by a billion years, the ancestors of present day cyanobacteria were the first dominant organisms to carry on oxygenic photosynthesis, involving a combination of membrane bound photosystems called photosystem I and II. The cyanobacteria probably evolved from certain ancestor bacteria that once carried out non-oxygenic photosynthesis by a single photosystem and by utilizing some inorganic compound other than water as a source of electrons and protons. Through the help of some external source of energy (sunlight), part of the inner membrane bordering the cell called the plasma membrane, which in cyanobacteria is located underneath both a cell wall and an outer membrane, can become folded inwardly to develop into a membrane system inside the cell; and the two photosystems, including sunlight-harvesting (light absorbing) units, can become embedded in such an internal membrane system. It is photosystem II that splits water and uses its extracted electrons and protons for reducing power and ATP to drive oxygenic photosynthesis. The new byproduct of photosystem II is oxygen, produced for the first time in abundance by the photosynthesis of cyanobacteria. These organisms were the first to carry out photosynthesis involving both photosystems I and II, and capable, therefore, of using light energy to extract electrons and protons from water, with the production of oxygen.

Beginning at the start of the Proterozoic Era (about 2.5 billion years ago), the organisms called cyanbacteria [by probably some time after 2.2 billion years ago (an estimate that varies with different authors)] changed the composition of the atmosphere (oxygen build-up) as well as the color of earth's sediments (due to oxidation of iron and other metals, leading to the banded iron formations or 'red beds' comprised of iron and other metal oxides). Although many bacteria were probably killed by the rising levels of oxygen in the atmosphere, organisms began to incorporate biochemical methods for rendering oxygen less harmful, leading to the evolution of aerobic or oxidative respiration (ability to employ oxygen in the process of cellular respiration = utilization via oxidative biochemistry of the energy stored in food for various other life processes). The cyanobacteria (soon after the origin of oxygenic photosynthesis) were probably the first to develop aerobic or oxidative respiration, which probably spread (via lateral gene transfer) from them to other unrelated bacteria.
Of course, the eukaryotes that indirectly take advantage of oxygenic photosynthesis by a partnership with other (unrelated) food producing organisms cannot be considered plants even by this broad definition. For example, the photosynthetic flatworm Symsagittifera roscoffensis (= Convoluta roscoffensis), as well as such organisms as photosynthetic corals, are not considered plants, because tiny single celled (oxygen generating) photoautotrophs only live in partnership within some of the cells of the host organisms in an unmerged relationship called symbiosis, which should be distinguished from genuine symbiogenesis (Mereschkovsky, 1905, 1910) that involves the eventual merging of at least two different symbiotic organisms into a single species. Lichens, although dual (plant plus fungus) organisms, are considered fungi and not plants, because their fungus part apparently has the upper hand, while dual (plant plus fungus) organisms like mycorrhizae are considered plants and not fungi, because the plant part is most conspicuous. Of course, photosynthetic flatworms and corals or lichens and mycorrhizae are symbiotic collections of at least two different organisms and not single organisms or species. However, if a cyanobacterium is first incorporated within a single cell of some non-photosynthetic eukaryote in the process of symbiosis as outlined above, the two formerly distinct organisms can eventually become merged into one organism in the very rare process of symbiogenesis. In the first eukaryotic plant, the cyanobacterium became integrated via symbiogenesis as a perminant organelle called the chloroplast with the ability (never found in internal symbionts) to import over a thousand different proteins from the rest of the host cell. Although thousands of genes were transferred from symbiont to the host nucleus, it is the specific import of proteins from the rest of the host cell and not the transfer of genes that actually integrates a symbiont as an organelle (Cavalier-Smith, 2007). An earlier symbiogenesis involving the endosymbiosis of some alpha-proteobacterium also took place (Muller, et al., 2012) in the origin of another organelle in the eukaryote cell called the mitochondrion, which now plays the critical role in aerobic (oxygen dependent) cellular respiration in nearly every eukaryote and the presence of this organelle (or vestiges of it called hydrogenosomes and mitosomes) is found in all eukaryotes. Although the particular, presently living members of the alpha-proteobacterium that are most closely related to the mitochonria are not yet certain, they are now narrowed down (according to some authorities) to non-photosynthetic, non-parasitic, not strictly aerobic alpha-proteobacteria somewhere within or closely related to the alpha-proteobacterial family Rhodospirillaceae (Degli Esposti, 2018). However, whether the alpha-proteobacteria incorporated as the mitochondia was originally a photosynthetic (eventually loosing this ability) or a non-photosynthetic organism is probably still an open question (Munoz-Gomez et al., 2017). Therefore, the eukaryote cell can be considered a chimaera, a single organism resulting from the integrative merging (through symbiogenesis) of the genes and gene products that originated from two or more originally distinct organisms. Such a chimaera (as a single organism or species) that can carry out oxygenic photosynthesis is obviously (by the broad definition) considered a plant.

However, the broad definition of plants (as those that carry out oxygenic photosynthesis versus those that do not) does pose certain problems. As a contradiction of this definition, isolated examples of non-photosynthetic types of plant parasites that are closely related to oxygen generating photoautotrophs have always been considered plants. For example, Monotropa uniflora (= Indian Pipe) in the blueberry family or some other non-photosynthetic types of plant parasites have always been considered plants that secondarily lost the need to carry on photosynthesis, because they are nested within groups of close relatives that do possess oxygenic photosynthesis. On the other hand, isolated examples, such as chlorarachniophytes and certain euglenoids that secondarily acquired oxygenic photosynthesis from other photosynthetic eukaryotes (see below), can be considered plants by the broad definition, even though they are nested within groups of close relatives that do not possess photosynthesis. The "chromophytes" [including chlorophyll c containing cryptophytes, haptophytes, heterokonts (= stramenopiles), and dinoflagellates] that by this broad definition are all considered plants (because they also secondarily acquired oxygenic photosynthesis) have apparently gaven rise (via multiple loses of photosynthesis) to numerous groups of non-photosynthetic organisms that are never considered plants. Therefore, although plants defined as organisms that directly carry out oxygenic photosynthesis form a functionally analogous group of organisms from the perspective of ecology (the study of the relationships between organisms and their environment), they are polyphyletic, comprising several distinct lineages that are not directly related to each other by descent from the same common ancestor.

In the broader definition of the plant kingdom, all simple water inhabiting or moist land dwelling organisms called "algae" (not a true lineage but rather a grade), whether "prokaryotes" or eukaryotes, together with more complex, dry land dwelling, oxygen generating photoautotrophs or their water inhabiting relatives are considered "plants." Traditionally, the so-called "thallophytes" [usually only spore producing organisms with a simple body type (thallus) not differentiated into shoot, root, or leaf parts, possessing a rigid wall around their cells] plus the more complex, dry land dwelling, spore or seed producing photoautotrophs (also with cell walls) were all considered "plants." The so-called "algae" (with absence of a well protected embryo, therefore, excluding all embryophytes) are the simpler, mostly water inhabiting or moist land dwelling "thallophytes" that are also oxygenic photoautotrophs. Another important character used traditionally to decide whether an organism should be considered a "plant" is lack of mobility or inability of the entire organism to move from place to place. This was another reason why the "thallophytes" originally often included the "bacteria," broadly defined "fungi," and all the "algae" (although some eubacteria and archaebacteria can possess motility via whip-tails that are not related to each other or to the flagella of eukaryotic "flagellates"). Many of these photoautotrophic or heterotrophic "thallophytes" with a relatively simple (undifferentiated) thallus, especially those with rigid cell walls and a relatively stationary life, depending on spores for reproduction, were considered plants. See mention of the old name "Thallophyta" above. However, today the broader definition of the plant kingdom is often restricted to lineages of oxygen generating photoautotrophs or certain isolated heterotrophic members of these lineages. The "thallophytes" that have been more commonly considered "plants" or "plant-like organisms" may include those with a plant body called a thallus (without true roots, stems or leaves), those (including all the "algae") with a fertilized egg (zygote) not developing into multicellular embryo within a protective female sex organ, and those "nonvascular plants" (without a water-conducting system of cells) like the "bryophytes" (liverworts, mosses, and hornworts).

Other authorities may want to limit plants to only those food producing creatures (photoautotrophs) considered eukaryotes (organisms with a well defined nucleus) that directly carry out oxygenic photosynthesis. This does not include "prokaryotes" (organisms without a well defined nucleus), such as the oxygen generating, food producing "bacteria" (i.e., cyanobacteria or blue-green algae). This also does not include organisms, such as corals, sponges, squids, or giant claims, that indirectly take advantage of oxygenic photosynthesis by a partnership with food producing dinoflagellates (more specifically referred to as zooxanthellae), which can actually live in comfort within the cells of their animal hosts; nor does it include certain protochordate invertebrate animals called didemnids and other colonial ascidians of tropical sea shores that harbor between their cells the cyanobacteria of the genus Prochloron. It also does not include organisms like the sea slug Elysia chlorotica that carry out photosynthesis within their cells by transient bodies called kleptoplastids bound by two membranes, because these transient bodies (temporarily kept alive but eventually digested) actually originate from an ingested photosynthetic stramenopile type algae identified as Vaucheria litorea. Some dinoflagellates also possess membrane bound kleptoplastids. Such a partnership is called endosymbiosis (a more or less mutually beneficial relationship between two organisms in which one, the endosymbiont, lives within the host cells). Although eukaryotes that can be referred to as plants, including many dinoflagellates, glaucophytes, diatoms, brown, yellow-green, and red algae, cryptophytes, haplophytes, and green plants, including "green algae" (a grade) together with the most common land plants, originally all come from non-food producing ancestors that started out by maintaining an endosymbiosis with other food producing bacteria or eukaryotes, the descendants of these host ancestors have permanently incorporated oxygenic photosynthesis into their lives by the conversion within their cells of the food producers (endosymbionts) into integral components called chloroplasts [light gathering chlorophyll (or other pigment) containing units or organelles] that are passed on from one generation to the next. The process of evolution by which this took place is further clarified below. Chloroplasts contain the pigments such as chlorophyll that absorb specific wavelengths of light inorder to convert it into the chemical energy possessed by sugar. Chloroplasts can also be modified to serve various other functions, such as specialized storage units for fats or sugars. Therefore, chloroplasts and all their modified forms are collectively referred to as plastids (see notes).

Because the plant kingdom as defined above includes many organisms that are not directly related to each other and some of these organisms have many heterotrophic (non-food producing) relatives, other authorities may want to define plants as all the descendants of the very first (primary-plastid) eukaryote to acquire oxygenic photosynthesis as an integral part of its cells by initially engulfing (via a process called phagocytosis) a cyanobacterium (a type of oxygen generating, food producing bacteria). Although the engulfed cyanobacterium initially only functioned as a partner within the host cells in the process called endosymbiosis, this food producing organism became established within each host cell and eventually became a permanent fixture, the first chloroplast [a permanent sunlight aided, food producing organelle = a functional component within the host cell(s)], that could be replicated during cell division and passed on to subsequent generations. Some evidence (although not conclusive) indicates that this event occurred only once in the history of life and, therefore, involves organisms that are (apparently) all directly related to the very first eukaryote ancestor to acquire oxygenic photosynthesis. If the plant kingdom is exclusively defined as the group of all descendants from the purported first eukaryote with photosynthesis, the other unrelated organisms that acquired photosynthesis did so secondarily by initially engulfing one or another descendant of this group. Primary endosymbiosis involved engulfment of a cyanobacterium by the ancestor of all plants [i.e., glaucophyes, rhodophytes (= red algae), and viridophytes (= green plants)], while secondary endosymbiosis involved engulfment of algae (that already had chloroplasts) by the various different ancestors of all the "plant-like" organisms. Therefore, all organisms with some "plant-like members" (e.g., dinoflagellates, diatoms, brown, and yellow-green algae, as well as chlorarachniophytes and certain euglenoids) that secondarily acquired photosynthesis can be considered outside the plant kingdom.
In the case above, the plant kingdom has been defined to include a proposed lineage called Archaeplastida Adl et al., 2005 (= Primoplantae J. D. Palmer, 2004), only including the Glaucophyta Skuja, 1954, commonly called glaucophytes, Rhodophyta Wettstein, 1901, 1922, commonly called red algae, and Chloroplastida Adl et al., 2005 (= Viridiplantae Cavalier-Smith, 1981), commonly called green plants or viridophytes. Note that dates are included together with authors in these optionally highlighted scientific names. These correspond to the publication dates of the names by the authors. The dates [like the author(s) names] are only optionally included but are sometimes useful in providing additional documentation in order to distinguish the same name that may have been applied to a different group of organisms by some other author(s) at some particular time(s).

Most but not all of the new DNA evidence, especially from multiple genes, supports a likely sister group relationship between Archaeplatida (including glaucophytes, rhodophytes, and viridophytes) and an expanded kingdom Chromista, rendering the traditional "chromists" [including only cryptophytes, haptophytes, and stramenopiles (comprising, among other groups, the diatoms and brown and golden and yellow-green algae)] paraphyletic. Because of additional new evidence from multiple genes, the kingdom Chromista has recently been expanded by T. Cavalier-Smith (2010) to include not only the original groups of stramenopiles (= heterokonts), cryptophytes (plus katablepharids), and haptophytes, but also the alveolates, rhizarians and centrohelid heliozoans, making the super group name 'chromalveolates' now unnecessary. However, at least some recent DNA evidence (from nucleus encoded protein genes) indicate that the Archaeplastida, as defined above for the plant kingdom, is an invalid lineage. For example, nucleus-encoded eukaryotic translation elongation factor 2 (EEF2) gene sequence evidence (Kim & Graham, 2008) has uncovered a well supported lineage (excluding stramenopiles and glaucophytes) that includes the certain "chromists" called cryptophytes (plus katablepharids) and haptophytes, as well as rhodophytes and Viridiplantae. This new DNA evidence renders both the Archaeplastida and the traditional "chromists" as questionable lineages. [This is another reason for restricting the plant kingdom to a smaller and more well supported lineage (like that of viridophytes or embryophytes).] Nevertheless, in most of the recent studies, especially when using DNA sequences from multiple genes, Archaeplastida appears to be a fairly well supported lineage (including only glaucophytes, rhodophytes, and viridophytes). See origin of plants. In most of these recent studies, there has been a consenus that stramenopiles group closest to the alveolates (including the dinoflagellates, malaria parasites, ciliates, and others); and stramenopiles + alveolates appear closest to the rhizarians (including many non-photosynthetic groups but also the chlorarachniophytes = green, amoeba-like algae with thin pseudopodia or cells bearing a single flagellum). All these plants or "plant-like organisms" are ancestrally biflagellates ("bikonts" with two flagella), although some members may secondarily bear only one flagellum or more than two flagella (with 'whip-like tails' for motility).

The "chromistan algae" or "chromophytes" [although nested within the (newly supported) expanded kingdom Chromista] do not form a uniform group of directly related photoautotrophs. Within this expanded kingdom, subgroups of algal organisms (the photoautotrophs) are scattered in their relationships among various subgroups of heterotrophs. The "chromistan algae" can now be said to include the not all directly related divisions Cryptophyta, Haptophyta, Chrysophyta, Xanthophyta, Bacillariophyta, Phaeophyta, Dinophyta, and Chlorarachniophyta.

On the basis of new DNA evidence involving multiple genes, the neozoan tree of life appears to stem from an ancestral grade of unicellular (single-celled) types of "bikonts" [with two flagella (like whip-tails) for motility] called core excavates with a rigid cell cortex (rigid peripheral part of cell just beneath the plasma membrane). The euglenozoans (euglenoids) also with a rigid cell cortex appear on one side of the eukaryote tree and core excavates plus neozoans on the other side. It is speculated that the eukaryote root may lie between the euglenozoans and core excavates plus neozoans or somewhere within the euglenozoans. Although euglenozoans may represent descendants from some of the earliest eukaryotes (if this depiction of the eukaryotic tree is the correct one), the ancestor of the phototrophic euglenozoans would have had to acquire its chloroplast via secondary endosymbiosis only after the emergance of the neozoan viridophytes (= green plants).

The characteritics of the proposed last common ancestor of all eukaryotes (with the exception of the chloroplast) share much in common with the presently living euglenoids. If this is the correct interpretation of the DNA evidence, the so-called animal and plant sides should apply only to the upper, neozoan part of the eukaryotic tree of life. The animal side may include Amoebozoa Luhe, 1913, emend. Cavalier-Smith, 1998, possibly Apusomonadidae Karpov and Mylnikov, 1989 (= Apusozoa), and Opisthokonta Cavalier-Smith, 1987, emend. Cavalier-Smith and Chao, 1995, emend. Adl et al., 2005. The plant side may include Archaeplatida Adl et al., 2005 sister to the kingdom Chromista Cavalier-Smith 1981 emend. The kingdom Chromista, as recently defined by Cavalier-Smith (2010), includes two major lineages: Hacrobia (= cryptophytes + katablepharids, centrohelid heliozoans, and haptophytes) and Harosa (= SAR group for stramenopiles + alveolates and rhizarians). Both these major lineages of Chromista consist of some plant-like organisms together with many (non-food producing) heterotrophs with a large number of green and/or red algae genes that may have come from endosymbiosis of these algae by the common ancestor of Chromista. A startlingly new discovery has recently been made (Moustafa et al., 2009) that all the major plant-like groups of Chromista (i.e., cryptophytes, haptophytes, stramenopiles, and alveolates) already long accepted to have acquired their chloroplasts via secondary endosymbiosis from a red alga also have over a thousand genes (in some cases) in their nuclei that apparently come from a non-streptophyte green alga (one that is not a streptophyte, probably a primitive, "protistan" viridophyte called a "prasinophyte"). No visible evidence of an ancestral green algal endosymbiosis survives today in the cells of most of these plant-like groups that is comparable to the chlorophyll containing plastids likely from an endosymbiosis of a red alga. However, among the rhizarians, there is a green algae derived chloroplast found in the cells of chlorarachniophytes. Of course, this interpretation of the eukaryote tree of life requires further testing with additional studies and at this point can still only be considered an educated guess based on all the evidence that is currently available.

Almost as old as the science of botany itself is the idea that the majority of the most familiar organisms called plants (those growing on drier land) originally come from an aquatic (water inhabiting) "green algae" ancestry. Therefore, other authorities may want to limit what are called plants to only those of the lineage commonly referred to as green plants (= viridophytes) and classified as the kingdom Chloroplastida Adl et al., 2005 = Chlorobionta Jeffrey 1982, emend. Bremer 1985, emend. Lewis and McCourt 2004 = Viridiplantae Cavalier-Smith, 1981. Included as an example in the notes page is an attempted classification of the kingdom of green plants (= viridophytes), with an emphasis on the families of the less derived members called "green algae" and the more derived members called flowering plants. This is a slightly modified, rank ordered classification system that is more or less consistent with that Lewis and Mc Court (2004) and Chase & Reveal (2009). The formal names listed (for kingdom, division, class, subclass, order, and family) include both authors and dates of publication. Many of the major lineages within the green plant kingdom are indicated by informal names preceding the formal names. Many of the formal names of these lineages are included under the formal family names listed in the dictionary. This is a kingdom composed of often bright grass-green organisms, including the two major lineages informally called green algae sensu stricto and the streptophytes sensu lato. Much DNA evidence indicates that green algae sensu stricto and streptophytes sensu lato are likely sister lineages. Therefore, green plants (viridophytes), although including the grade of "green algae" + the lineage of land plants (embryophytes), are more usefully divided into two major lineages, often classified as the divisions Chlorophyta Reichenbach, 1828, emend. Pascher, 1914, emend. Lewis & McCourt, 2004 (green algae sensu stricto) and Streptophyta Jeffrey 1967, sensu Leliaert et al. 2012 (= streptophytes sensu lato = Streptophyta Bremer, 1985 or Charophyta sensu Karol et al., 2001).
Note that certain Latin words besides the authors and dates can be sometimes incorporated into the scientific names. The abbreviation emend. (for the Latin word emendatio) means a correction or amendment. These additions might also include Latin phrases, such as sensu lato (abbreviated s.l.) or sensu stricto (abbreviated s.str. or s.s.), distinguishing a broader or more inclusive and a narrower or more exclusive grouping, respectively. The Latin word sensu means 'in the sense of,' while sensu lato means 'in the broad sense' and sensu stricto means 'in the narrow or strict sense.' As in the author(s) and dates of publication of a scientific name, these additional Latin words or phases are optionally included in the name. This convention can often be used for informal names of various groups.
For example, the grades called "green algae sensu lato" (including the lineage of green algae sensu stricto + "streptophyte green algae") and "streptophyte green algae" alone are considered artificial groups, because they both do not include all descendants (i.e., green land plants called embryophytes) from a common ancestor. The quotation marks indicate that a group is by itself artificial (not a true lineage) and often applies to a grade. Although Bremer et al. (1987) assigned the division name Streptophyta to "streptophyte green algae" plus green land plants, Jeffrey (1982) had already used this name (therefore, given priority by ICBN) to include only stoneworts (order Charales Lindley, 1836) plus embryophytes (land plants), both together once often referred to as the subdivision Streptophytina Lewis & McCourt, 2004. This has generated some potential confusion regarding certain names. The division Charophyta Kenrick & Crane, 1997 (= Charophyta Karol et al., 2001, emend. Lewis and McCourt, 2004) is now often referred to as charophytes sensu stricto or stoneworts (order Charales). However, this division is not the same as the much broader division Charophyta sensu Karol et al., 2001, which includes all "streptophyte green algae" (not just stoneworts) plus embryophytes. Furthermore, the charophytes s.s. are no longer commonly considered the sister group of embryophytes. As the DNA of more and more genes are being sequenced, analyses are now commonly providing evidence that the conjugates and not the charophytes s.s. are sister to embryophytes (land plants).

The division of streptophytes s.l. (formally named Streptophyta Bremer, 1985 = Streptophyta Jeffrey 1967, sensu Leliaert et al. 2012) can be defined (as done above) to include "streptophyte green algae" (a grade) plus land plants. Some of the "streptophyte green algae" (also called "charophycean algae") do not possess a phragmoplast [a structure that appears during cell division between the two (duplicated) nuclei that consists of minute protein tubules (microtubules) and minute membrane-bound (sack-like) vesicles]. The phragmoplast is often treated as a possible shared derived character that is found in the lineage of phragmoplastophytes, including some streptophytes and all land plants. Although the "streptophyte green algae" plus land plants may form a valid lineage (even though "streptophyte green algae" by themselves do not, because they exclude land plants), some authors () have suggested that possible problems in applying names can be avoided by defining as streptophytes only those organisms (ancestrally) with all members possessing a phragmoplast, including charophytes sensu stricto plus land plants. This was the proported lineage of streptophytes sensu stricto or the subdivision Streptophytina Lewis & McCourt, 2004. Even though some members of the class Coleochaetophyceae Bessey ex Woods, 1894 (often called coleochaetophytes) are known to possess a phragmoplast, all members do not; and the class Zygnematophyceae Round, 1971 (often called conjugates) only show signs in certain members of possessing such a structure. The debate on the closest sister group to land plants is still not settled, although there is considerable DNA evidence involving multiple genes that this sister lineage might possibly be the conjugates with only some members [e.g., the genus Spirogyra Link in C. G. Nees (1820) of the paraphyletic order "Zygnematales" C.E.Bessey, 1907 and polyphyletic family "Zygnemataceae" Kutzing, 1843] only possessing a phragmoplast-like structure.

The reader should be aware that streptophytes sensu lato usually applies to a broader or more inclusive group (usually all the "streptophyte green algae" plus all the land plants), while streptophytes sensu stricto has been applied to more narrowly defined (more exclusive) group of streptophytes that includes the embryophytes plus the group thought to be sister to the embryophytes. There is further discussion (above) on the meaning of the Latin phrases sensu lato or sensu stricto. Also, some authors in the past have used the name "charophytes" to refer only to the green plant classes Coleochaetophyceae Bessey ex Woods, 1894 and Charophyceae Rabenhorst, 1863 (distinguishing these relatively more complex algae from Zygnematophyceae Round, 1971 and other "streptophyte green algae"), while others have applied the name "charophytes" to the entire grade of "streptophyte green algae" (not including land plants). Although the closest living relatives sister to land plants (embryophytes) is still in debate by authorities, considerable new evidence (some from multiple genes) seems to be singling out the Zygnematophyceae (including the conjugates, such as Spirogyra and relatives) as the most likely candidate sister group of embryophyte. See preferred streptophyte tree according to this recent evidence. If this new evidence continues to gain support, the streptophytes sensu stricto of Lewis and McCourt (2004) will no longer be supported as a valid lineage. This is the subdivision Streptophytina Lewis & McCourt, 2004. The creation of this subdivision was based the now falsified assumption that Charophyceae comprise closest living relatives sister to land plants. The reader should also be aware that Charophyta Karol et al., 2001, emend. Lewis and McCourt, 2004 = Charophyta Kenrick & Crane, 1997 (comprising only the order Charales) is not the same as Charophyta sensu Karol et al., 2001. In the classification of Karol, et al. (2001), "The Charophyta comprise the land plants and at least five lineages (orders) of fresh water green algae, and are sister to the Chlorophyta, which consist of essentially all other green algae." This applies (as outlined above) to Charophyta sensu Karol et al., 2001 (= streptophytes sensu lato) that are sister to Chlorophyta Pascher, 1914, emend. Lewis and Mc Court, 2004 (= green algae or chlorophytes sensu stricto). Fortunately, not all scientific names become associated with such complications (although some others can be worse).

Still other authorities may want to limit the plant kingdom only to the green plants (= viridophytes) commonly called land plants (= embryophytes). These are mostly photoautotrophic organisms (with green chloroplasts and oxygenic photosynthesis) that arose when descendants of some freshwater inhabiting, green plant ancestor of the paraphyletic group of "streptophyte algae" invaded the drier land, and developed from the fertilized, unicellular (single celled) egg called the zygote a unique, enclosed and well protected, multicellular (many celled) embryo. In all presently living land plants, the embryo arises from successive cell division of zygote as the first stage in the development the sporophyte (the multicellular plant that at maturity produces the spores). This is why it is better to refer to these land dwelling plants as embryophytes. This name 'embryophyte' applies to photoautotrophs that produce from a single fertilized egg cell (zygote) a young embryo sporophyte nurtured and protected at least during the early stages of its multicellular development within the tissues of the parent gametophyte. This embedding of the embryo for nourishment and protection within the tissues of the parent gametophyte can be considered a shared, divergent character from which the name 'embryophyte' derives. This character helps to distinguish members of this lineage of land plants from "algae". However, in order to more fully grasp what is meant by this character and how it applies to all groups within the lineage, the reader is advised to check out the more detailed discussions on alternation of generations involving the development of two (more or less) distinct plants called the sporophyte and gametophyte found in most embryophyte species that can carry out sexual reproduction. See also land plants defined, the nature of embryophyte spores, vascular plants, the difference between "free-sporing plants" and seed plants, flowering seed plants (= angiosperms), and the currently preferred genealolgical tree hypothesis for embryophytes. For classification consistent with APG with an emphasis on flowering seed plants, see land plants, bryophytes, vascular plants, lycophytes, euphyllophytes, monilophytes, seed plants, gymnosperms, and angiosperms.

Today, what is referred to as plant science is often restricted to the study of embryophytes (often less precisely referred to as land plants that are as a whole most closely related to "streptophyte algae" also called "charophycean green algae" (CGA). This restriction is currently embraced by many botanists, because the definition of the boundry or limits of what should be considered the plant kingdom is still being debated. Therefore, in the discussion of the earliest colonization of land (terrestrialization) by organisms of aquatic (salt or fresh water) origin that possibly first began more than a billion years ago, the land adapted "algae" are often distinguished from what is referred to as the first plants. These first plants are often assumed to have included the embryophyte ancestors of both bryophytes and 'polysporangiophytes'. However, the possible embryophyte progenitors known only from sporopollenin-impregnated microfossils called cryptospores could have colonized land prior to the origin of the embryo/sporophyte characteristic of embryophytes. Presently, there are also several organisms of the green plant or viridophyte lineage (including a few streptophytes) other than embryophytes that can be considered terrestrial (land dwelling) photoautotrophs. Although the restriction of the study of what are rather arbitrarily called plants to the dominant land dwelling embryophytes should probably better be referred to by some other name besides 'plant science'. this can be contrasted with traditional botany as the study of "bacteria" ("prokaryotes", including, among others, photoautotrophs called cyanobacteria), almost all eukaryotes that can be considered photoautotrophs (various groups of "algae" and, of course, land plants), or any relatively stationary eukaryotes with spores and cell walls that can be considered heterotrophs other than the usually more mobile animals without spores and cell walls. The heterotrophs of traditional botany included many "bacteria" and the eukaryotes, such as broadly defined "fungi" (= true fungi plus "fungi-like" organisms, and different types of "slime molds"). Even though many of the organisms traditionally called "crytogams" (including fungi) have been adopted by microbiology, botany is still taught today in some schools, universities, or colleges from this traditional broad scope, including many other organisms besides those that are considered by most people to be plants. The rules for naming such a broad scope of organisms (including at least fungi and cyanobacteria together with any oxygenic photosynthetic eukaryote not considered an animal) are still under the influence of the International Code of Botanical Nomenclature or ICBN. However, although the naming of cyanobacteria is still under ICBN, there is now (since 1980) a separate Code (ICNB) for cyanobacteria and other "bacteria". See also different definitions of what could constitute the plant kingdom.

Origin of "Plants"

Cyanobacteria are the only prokaryotes that perform oxygenic photosynthesis, which was first eventually transmitted via endosymbiosis as the chloroplast to the ancestor of all the primary-plastid (photoautotrophic) eukaryotes. Phylogenomic, trait evolution, and molecular clock analyses of Sanchez-Baracaldo (2015) appear to support a freshwater origin of Cyanobacteria possibly 1,600 to 1,000 million years ago (Mya). It is currently estimated that a freshwater, heterotrophic unicellular eukaryote ancestor engulfed the primary-plastid from an early-branching, freshwater cyanobacterium about 1,500 Mya (De Vries & Archibald, 2017). A recently discovered presently living, freshwater cyanobacterium Gloeomargarita lithophora has been found to be a member of an early branching lineage that links closest to the lineage of plastids [to the exclusion of other (known) Cyanobacteria] on genealogical trees reconstructed using DNA genomic sequences for plastid-encoded and nucleus-encoded proteins (Ponce-Toledo et al., 2017). The major primary acquisition of plastids (e.g., chloroplasts) by Chloroplastida (green plants, including "green algae" and embryophytes), Glaucophyta (Cyanophora), and Rhodophyta (red algae) has been fairly well established to be monophyletic (Rodriguez-Ezpeleta et al., 2005). Although monophyly of this primary acquisition of plastids (a single endosymbiosis of a cyanobacterium by a heterotrophic eukaryotic host) has been fairly well supported by extensive phylogenomic analyses (Deschamps & Moreira, 2009), the relationship between plastid bearing lineages and their placement on phylogenetic trees of extant Cyanobacteria have been controversial. By careful reconstruction of a phylogenomic trees for extant (presently living) Cyanobacteria and primary photosynthetic eukaryotes (Archaeplastida), ancestral character state reconstruction, and placement of the chloroplast bearing eukaryotes on the trees, convincing evidence has been provided that basal Cyanobacteria may have originated in inland freshwater environments and that subsequent endosymbiosis of a cyanobacterium by the ancestor of Archaeplastida may have occurred at a time when Cyanobacteria were still restricted to freshwater, with some of the more derived members of Cyanobacteria and Archaeplastida only later (secondarily!) invading the sea (Blank, 2013a, 2013b; Blank and Sanchez-Baracaldo, 2010; Delwiche & Cooper, 2015; Sanchez-Baracaldo et al., 2005; Sanchez-Baracaldo, 2015). A freshwater origin of both Cyanobacteria and primary-plastid eukaryotes is also supported by the observation that the basal tree branches of Cyanobacteria, Chloroplastida, and Rhodophyta, plus Cyanophora, are presently represented by freshwater organisms; and most of the marine organisms represent more derived branches! If plastids had a freshwater origin, are marine algae only secondarily marine organisms? This question has recently come to the foreground (Delwiche & Cooper, 2015), even though it is still almost universially accepted and probably correct that fungi and animals, as well as the heterotrophic ancestors of plants, were originally (at some remote point in their origins) all (ultimately) unicellular marine microbes (Berbee, James, and Strullu-Derrien, 2017). It is also almost certain that land plants descend from an inland, freshwater, streptophyte (charophycean) algal ancestor. The progenitors of such an ancestor may (?) have inhabited inland freshwater early in the Neoproterozic before some of the other types of red and green algae (rhodophytes and chlorophytes) and even Cyanobacteria spread from freshwater into the sea. All known "streptophyte (charophyte) green algae" have apparently remained freshwater organisms; and they almost certainly descend from a very ancient, inland, freshwater lineage (De Vries et al., 2016).

Although the naming of fungi is still under the Botanical (ICBN) Code, there are a few slight differences in some of the suffixes of the rank names. For ranked groups of fungi, the suffixes are -aceae for family, -ales for order, -mycetidae for subclass, -mycetes for class, -mycotina for subphylum, and -mycota for phylum (except for the phylum of parasites called Microsporidia Balbiani C. R.). Compare this with the normal scheme for naming plants. The phylum name Chytridiomycota M. J. Powell is retained in the recent classification system of Hibbett, et al. (2007), but the name is restricted to the class Chytridiomycetes Caval.-Sm. (including orders Chytridiales Cohn, Rhizophydiales Letcher, and Spizellomycetales D. J. S. Barr) and the class Monoblepharidomycetes J. H. Schaffn. (including single order Monoblepharidales J. Schr�t.). In this classification, certain traditional "chytrids" are separated from Chytridiomycota and placed in their own phyla: Neocallimastigomycota M. J. Powell, and Blastocladiomycota T. Y. James. Hibbett, et al. (2007) does not consider the phylum "Zygomycota" a valid toxonomic group, treating as separate the phylum Glomeromycota C. Walker & A. Schubler and several subphyla, including Mucoromycotina Benny, Entomophthoromycotina Humber, Kickxellomycotina Benny, and Zoopagomycotina Benny. The last mentioned subphyla remain unplaced in any phylum. The genera Caulochytrium, Olpidium, and Rozella, once placed in the traditional "Chytridiomycota", and the genus Basidiobolus, once placed in the now abandoned order Entomophthorales of "Zygomycota", remain unplaced in any higher ranking group. The fungal subkingdom called Dikarya Hibbett, T.Y. James & Vilgalys (= Neomycota Cavl.-Sm.) includes the two phyla Ascomycota Bold ex Caval.-Sm. and Basidiomycota Bold ex R. T. Moore; and, of course, the kingdom is Fungi. The current full name of the fungal kingdom is Fungi T.L. Jahn & F.F. Jahn ex R.T. Moore. The word "ex" means "validly published by." Fungi, as the name of one of six kingdoms of life, was introduced by Jahn & Jahn in 1949. The name was also used in a five kingdom system of classification advanced by Whittaker in 1959 and 1969. However, neither of these authors included a Latin diagnosis. Therefore, the name was invalid under the ICBN Code until the required Latin was provided by Moore in 1980. Even though there are other subgroups of fungi, the subkingdom Dikarya is probably the most important group from the medicinal point of view, including most (if not all) of the known medicinal lichens, molds, and mushrooms (with certain fungi outside this group only sometimes employed to produce the medicinal chemicals called steroids). The Latin diagnosis for the subkingdom name Dikarya was provided by Hibbett, et al. (2007). The use of this name is consistent with that of James, et al., Vilgalys (2006). Bold in 1957 appears to be the first to propose the phylum name Ascomycota. However, Bold did not include a Latin diagnosis, and a very short, two worded Latin diagnosis ("sporae intracellulares") was later provided for the name by T. Cavalier-Smith in 1998. Again, Bold is acknowledged for proposing in 1957 the name Basidiomycota, which in turn was validated with a Latin diagnosis by Moore in 1980. This gives the reader a few examples of how the history of names can be traced by way of their optionally included authors. This is the reason why dates of publication are also optionally included with the author names. See examples involving dates for certain names in the plant kingdom.

The kingdom Fungi can be defined as a combination of at least 6 characters. They are (1) always eukaryotes [possessing within their cells functional units called organelles that are often membrane bound (e.g., the double membrane bound nucleus, containing most of the genes and chromosomes)]; (2) each of their cells are surrounded by a wall usually made of variable amounts of a resistant material called chitin [made up of many nitrogen containing (modified) sugar (N-acetyl-glucosamine) units], other materials containing linked (unmodified) sugar units called alpha- and beta-glucans, and some proteins called glycoproteins, containing short side chains of linked (unmodified) sugar units; (3) they can form a multicellular body called a mycelium [a network of branching filaments (narrow, elongated chains of cells called hyphae)] or they can exist as single cells (e.g., yeasts); (4) they reproduce by (often) aerial spores (those disseminated by air currents) or (only in "chytrids") zoospores [motile (swimming) spores, each propelled by a single posterior flagellum]; and (5) they are heterotrophs (e.g., saprobes, parasites, or symbionts) that (6) all selectively feed by absorption [= osmotrophy - secreting exoenzymes on food and absorbing the simple nutrient substances dissolved in water that result from the externally digested food material]. Absorption can generally be said to involve the uptake of small nutrient substances by the body of an organism. In fungi, this is osmotrophy (selective absorption of simple, externally digested nutrients). In the osmotrophy of many filamentous fungi [most of which are primarily saprotrophs (= saprobes ~= decompsers)], a large amount of exoenzyme secretion occurs across the cell membranes via the process called exocytosis, while absorption of digested nutrient substances occurs across the cell membranes via the processes called pinocytosis and receptor-mediated types of endocytosis, and active transport. However, in many yeasts, osmotrophy occurs with little or no secretion of exoenzymes. See fungi and plants and osmotrophy.

If organisms possess all six characteristics that are mentioned above (not just one or a few of these character but all of them, together), the chances are that these organisms are members of the kingdom Fungi is relatively high. However, if not all these characters can be applied (because they may not always be easily observed without a microscope or some other technical means of testing for their occurrence), the organisms examined (although possessing many of these characters) may end up being members of various unrelated groups with several fungus-like features. Such organisms (from the standpoint of ecology) may even have similar or almost identical functions as the true fungi in the environment; and many of these "fungus-like creatures" were once often (traditionally) grouped together with the true fungi. Organisms that carry on osmotrophy are said to be osmotrophic. Although all fungi are osmotrophic, most are saprotrophs, and none undergo phagocytosis or ingest food in any other way, the nutritional mode osmotrophy alone does not distinguish fungi from all other organisms. Even though most animals carry on phagocytosis or ingest food in some other way and lack cell walls, there are at least some that are osmotrophic. As a primitive character found in many unrelated organisms, osmotrophy is more widespread than phagocytosis (or phagotrophy = ingesting or engulfing food), which is restricted to only eukaryotes (organisms with a well defined nucleus). Phagocytosis or filter feeding (= suspension feeding, obtaining food from the particles suspended in the water) can be found in sponges, "protozoa" and "coelenterates." Unlike fungi, many animals ingest larger food particles, but like fungi, animals can carry on extracellular (outside cell) digestion by exporting or secreting digestive enzymes and, in turn, taking up the resulting soluble nutrients by osmotrophy. However, unlike fungi, extracellular digestion and osmotrophy in animals usually takes place within a digestive tract. Nevertheless, it appears that fungi and animals are more alike and closely related than was once thought: they both share the ability (through exocytosis) to export proteins called digestive enzymes that break down (or digest) food through hydrolysis (the breaking of chemical bonds, through the addition of water); they can both take up the simpler digested nutrients by osmotrophy; they both store their food energy as glycogen; they are both often composed of structures made of chitin; a protein called collagen has been found in some fungi and almost all animals (but not elsewhere); and they both have certain cells with a single flagellum that (when present) beats behind these cells. There are also many unrelated organisms, such as certain "prokaryotes" (= "bacteria" = organisms without a well defined nucleus) and some eukaryotes, including certain single-celled "protozoans" and several multiple-celled, "fungus-like organisms," that use osmotrophy as their principal mode of nutrition. In order to distinguish fungi from other functionally similar, "fungus-like eukaryotes," such as oomycetes (water molds and downy mildews), corallochytrids, hyphochytrids, thraustochytrids, cellular slime molds, plasmodial slime molds, other types of slime molds (such as the acrasids, copromyxids, and fonticulids), and the plasmodiophorids (= plasmodiophoromycetes) that are parasites of certain plants, there are several much more technical distinctions that should probably be added to the 6 characters listed above. This will not be attempted here, but will be covered in more detail by at least one additional paragraph on a page to be added to the dictionary. Many of the "fungus-like organisms" (e.g., corallochytrids, hyphochytrids, labyrinthulids, oomycetes, and thraustochytrids) acquired cell walls and evolved osmotrophy independently of the entire kingdom Fungi. Most slime molds and plasmodiophorids have often been considered "protozoans." These are amoeba-like organisms (unrelated to each other and to kingdom Fungi) that have independently acquired aerial spores similar (convergent) to those of Fungi. See examples of independent (convergent) evolution. At this point, the reader should at least appreciate that precise definitions of whole kingdoms of organisms, such as fungi, plants, or other types, are not always that easy. This is especially true, the more inclusive the kingdoms become. In the history of biology and solely on the basis of anatomy or morphology, it has almost always been difficult to define clearly any of the higher levels of taxonomic rank; and it has largely been found impossible to do so for many of the earliest fossil groups.

Since traditionally the animals included almost all the "protozoa" and the "plants" included land plants, as well as collectively, the "thallophytes" (fungi, "fungus-like" organisms, "algae" and certain "bacteria"), the naming of these organisms has been subject exclusively to either the Zoological Code or the Botanical Code, an arrangement which was strongly influenced by the 17th century, two kingdom system of life originally popularized in the 18th century by Linnaeus. Although both the International Code of Botanical Nomenclature (ICBN) and the International Code of Zoological Nomenclature (ICZN) were originally based on similar objectives that there should be (ideally) a unique name for each rank (= taxonomic category = taxon), this name should be the same worldwide, independent of the any particular language, and the choice of competing names should be determined by precedence in date of publication, these two Codes diverged in the mid-19th century. Furthermore, in the 1950s the bacteriologists (those that study "bacteria") set up their own Code based on the Botanical Code that they had previously followed. This Bacteriological Code (BC) first became official in 1973 (with a new starting date), as an offshoot of the ICBN. As a consequence, the blue-green algae (= cyanobacteria) are now treated under both the Botanical (ICBN) and Bacteriological (ICNB) Codes.

The International Code of Botanical Nomenclature (ICBN) is actually the former name for the International Code of Nomenclature for algae, fungi, and plants (ICN), which is a collection of rules and recommendations for formally naming groups of organisms that have been traditionally treated as "algae", "fungi", or "plants". The former code (ICBN) was changed in 2011 by the International Botanical Congress in Melbourne (the capital city of the state of Victoria in Australia), and this changed code became part of the Melbourne Code that replaced the prior Vienna Code of 2005. The Shenzhen Code adopted in 2017 by the International Botanical Congress held in Shenzhen, China is now consider the current code.

Today, classification systems with formal names are more often based (as much as possible) on a proposed nested hierarchy of lineages, which are groups within broader groups within even broader groups, etc. that are (at least ideally) neither polyphyletic (not all necessarily directly related by a single common ancestry) nor paraphyletic (not comprising all descendants), although (according to a few modern authorities) the existence of a certain number of paraphyletic groups in classification is sometimes (in practice) unavoidable. See more on this below for microbes. [Another example is the current acceptance of a paraphyletic subtribe "Carduinae" (Cass.) Dumort. of the tribe Cardueae Cassini (= Thistles) in the family Asteraceae (see Cardueae Tree).] Because of this recent trend to formally name only monophyletic groups (single common ancestor together with all its descendents), some older formal names can now be invalidated and newer ones published (along with a Latin diagnosis) provided that the older names represent invalid lineages and the newer ones represent valid lineages previously unnamed. A brief, nested hierarchy of lineages is given for each family listed in the dictionary. Links will evidentially be included to an additional web page with formal names for these lineages (if published) and a description of each lineage in terms of shared derived or other diagnostic characters. An example of a nested hierarchy of informal names of lineages including the flowering plant family Asteraceae is given below.

The history of taxonomic biology (~= systematics) and the subdivision called taxonomic botany can be summarized as a history of formal and informal names. Although many of these names are now recognized as invalid (not true lineages), the reader that chooses to access the older literature on medicinal resources should at least be introduced to some of these older names in order to develop some insight on the nature of valid versus invalid names. Furthermore, some names presently considered invalid by most authors are still occasionally used in classification by some authors (e.g., "Algae" or "Pteridophyta"). They are often also informally employed to characterized organisms of unrelated lineages with roughly the same grade or level of complexity. The capitalized group names mentioned in this web page in quotes that are in bold print, although once formally recognized and (some of them) still recognized as such by some biologists, are now largely considered polyphyletic or at least paraphyletic and often no longer formally recognized. Sometimes quotes are also placed around informal names (here, sometimes not capitalized or at least not in bold print or not italicized) for the same reason of indicating that they represent names of groups currently not considered valid (i.e., not true lineages). Therefore, quote marks surrounding a formal or informal name for a group of organisms or surrounding a short phrase describing this group (as an alternative to a name) are used here to signify that this name or phrase does not apply to a true lineage, but it applies to an artificial group that has more recently been found to be either polyphyletic or paraphyletic. Formal or informal but artificial group names in quotes can also be retained in a classification system pending further study and subsequent revisions. This summary starts with the older two or three kingdom classification system of life and culminates with the most recent three domain hypothesis for the entire the tree of life, including "prokaryotes" and eukaryotes. The more recent hypothesis for the eukaryote tree of life is also outlined (the reader is not expected to fully understand all the groups of this vast assemblage). From this historical prospective, there are several attempts to define "plants" at the level of kingdom.

Only in relatively recent times (discussed more later on this page), the the better understood eukaryotes called "macroorganisms" (especially the multicellular ones, such as land plants and animals) began to be distinguished from the often less understood, "left-over" organisms now often referred to as the "microorganisms" ["fungi" (including true fungi + "fungus-like organisms") + the predominantly unicellular but sometimes multicellular "protists" ("algae" + "protozoa") and the rarely multicellular "prokaryotes"]. This ultimately misleading but often initially helpful trend in biological science to distinguish (and in turn segregate) better understood from less understood organisms may even apply (here and there) to the modern attempts to reconstruct the tree of life.

Since all organisms were once upon a time classified as either "plants" or animals, the less understood "fungi" (true fungi and "fungus-like organisms"), as well as "bacteria" ("prokaryotes") and "algae" (all oxigenic photoautotrophs without well protected embryos), were classified in the plant kingdom, based mainly on the presence of a cell wall, immobility, and the lack of any ingestion of food material (no phagotrophy). These were the least understood "crytogams" of the plant kingdom, including the "plant-like organisms" later called the "thallophytes" (those without well defined organs called leaves, stems, and roots). They were grouped together with other not well understood "crytogams" called "bryophytes" ("moss-like land plants") and "pteridophytes" ("fern-like land plants") plus the better understood and more conspicuous phanerogams (seed plants).

In the history of botany, those 'higher' forms (like seed plants, especially flowering plants) that comprise the most common, conspicuous, or useful elements of the plant kingdom (however defined) were studied first; and the less conspicuous and often simpler forms were frequently defined as all the "left over organisms" without the characteristics of the 'higher' ones (Bower, Drummond, Bond, & Wardlaw, 1947). At the time of Linnaeus, there were recognized the more conspicuous seed plants called phanerogams (from the Greek phaneros, meaning 'visible') versus the left over or less understood seedless plants called "cryptogams" (from the Greek kryptos, meaning 'hidden'). The word gamos (meaning 'marriage') was combined with phaneros or cryptos. During and prior to the time of Linnaeus, almost everyone believed that all plants possess flowers and fruits. Therefore, all the phanerogams (seed plants) were initially thought to exclusively comprise the more common and conspicuous flowering plants (today often called angiosperms). The means of sexual reproduction in the left over plants called "cryptogams" was not that apparent even much later to 19th-century botanists. These were plants or "plant-like organisms" that produced only dust-like spores and never seeds. The distinction between phanerogams and "cryptogams" began to be defined prior to Linnaeus as focus on reproductive features called fructification in plant classification became more emphasized. See Gesner, Cesalpino, John Ray, and Tournefort. Although it is now known that the evolutionary succession of many other events must be explained to get an understanding of trees or the flowers and fruits of the herbs, shrubs, and trees of angiosperms, these were some of the first more conspicuous plants or plant parts to be recognized and studied. However, in order to truly understand trees, and the flowers and fruits of the herbs, shrubs, and trees of angiosperms, the historic (evolutionary) perspective is necessary, concentrating on successive descent with modification that led to the simplest, initially least understood "steptophyte green algae" and land plants from earlier forms of life that were even less understood until recently. It is now known that this step by step evolution or descent with modification of plants started about 4 billion years ago with very simple life forms and has culminated in the relatively recent dominance of angiosperms on land from the Cretaceous to the present.

By the 20th century, G. M. Smith's Cryptogamic Botany, McGraw-Hill, New York, treated "Algae" plus "Fungi" in Volume I (1938) and "bryophytes" (mosses or "moss-like plants") plus "pteridophytes" (ferns or "fern-like plants") in Volume II (1955). The merging together of the less understood plants often resulted in "artificial groups" of left over organisms that are now considered polyphyletic (not all directly related by a single common ancestry) or paraphyletic (not comprising all descendants). For example, as this process continued, the entire group of better understood organisms called embryophytes (~= land plants) were contrasted with the less understood (left over) "plants" referred to as "Thallophyta". Since the fertilized egg (called the zygote) of most land plants, during the early stages of development, becomes a multicellular embryo and the embryo is either protected within a female sex organ or within the seed, the "Thallophyta" were defined as those "plants" with zygote not developing into a multicellular embryo within a protective female sex organ or seed.
Unlike the majority of land plants, the polyphyletic "Thallophyta" do not possess true roots, stems or leaves and they are typically nonvascular (without a well-defined water-conducting system of cells called the xylem). There was also proposed a group of 'lower' forms called Bryophyta s.l. (liverworts, mosses, and hornworts, now considered possibly monophyletic) of 'more or less thalloid embryophytes' (with protected multicellular embryos but without roots and no xylem). The Bryophyta s.l. [treated until very recently (2018) as an invalid (paraphyletic) taxon or artifial taxonomic group by many modern botanists but now considered likely monophyletic) was said to be composed of organisms 'higher' than "Thallophyta" but 'lower' than Tracheophyta (= vascular plants). Most of the 'more or less thalloid land plants' (those sometimes without leaves or shoot and never with a root) were once placed in the group called Bryophyta, defined as those embryophytes that lack well-defined water conducting cells called tracheids (a diagnostic or defining character for vascular plants). All those superficially similar embryophyte land plants including Lycopodiophyta (= lycophytes), as well as the ferns and horsetails with tracheids but that lack seeds were placed in the now considered polyphyletic group called "Pteridophyta". See also living members of the group called "pteropsids" (including only ferns plus cycads, the genus Ginkgo, conifers, gnetophytes, and angiosperms). Such classification systems for "plants" (including the above, now considered artificial groups with formal names here highlighted and in quotes) were once common throughout the first half of the 20th century (e.g., Bower, Drummond, Bond, & Wardlaw, 1947).

The "Thallophyta" (as part of the "plant kingdom" of the old two kingdom system of life) is now considered an artificial residuum of all so-called "plant-like organisms" (those traditionally treated as "plants") other than the embryophytes (most of the land plants). Such a residuum (now considered a "garbage heap" of only superficially similar elements) can be thought of as a left over group of less distinctive, often not directly related, and often less conspicuous or little understood organism defined solely on the basis of what they lack compared to a more distinctive, often more conspicuous, and better defined group. The residuum called "Thallophyta" was composed solely of the "plant-like thalloid organisms" (those simpler, not necessarily directly related ones without differentiated leaves, shoot, or root). Originally, this group excluded only the animals and the "animal-like protozoans." Therefore, it included not only the "algae" plus cyanobacteria (traditionally considered blue-green algae) but also the fungi, "fungus-like organisms" (traditionally treated as fungi), and often also the "bacteria." The system proposed by Eichler in 1886 was widely adopted and still has (in more or less modified form) influence on the classification systems in some present-day textbooks. In his system, most unicellular organisms ("protists" possibly not distinguished from "bacteria") are apparently excluded from the "thallophytes"; but all plant divisions other than that of the "thallophytes" is not recognized by him collectively as a higher level group (now called Embryophyta).

As late as 1960, Arthur Conquest divided "plants" into two major groups: "Thallophyta" and Embryophyta. The second group called Embryophyta included Spermatophyta - seed plants [Anthophyta (flowering plants) and Gymnospermae - nonflowering seed plants (Cyadophyta - cycads and Coniferophyta - conifers)], "Pteridophyta" [Filicophyta (Filices - ferns), Calamophyta (Equisetae - horsetails), Lepidophyta (Lycopodiae - clubmosses or spikemosses), and Psilophyta (Psilotae - whisk ferns)], and "Bryophyta" [Anthocerotae (hornworts), Hepaticae (liverworts), and Musci (mosses)]. The first group called "Thallophyta" included "Fungi" (true fungi and "fungus-like organisms"), "Algae" (Phaeophyta, Chrysophyta, Pyrrophyta, Rhodophyta, Euglenophyta, "Chlorophyta," and Cyanophyceae), and "Schizophyta" (Cyanophyceae and "Bacteria"). The cyanobacteria of class Cyanophyceae were considered "algae" and at the same time considered (together with the non-algal "Bacteria") members of "Schizophyta" [a name proposed by Cohn (1875) for life forms distinct from all eukaryotes]. Recognizing it as somewhat speculative, Conquest represented this classification as what he called a phylogenetic tree, useful in helping to keep organized scientific knowledge about various kinds of "plants" to facilitate information retrieval. In a diagram of the tree proposed by Conquest (1960), it was indicated that within the "green algae" (division "Chlorophyta") the class Chlorophyceae (e.g., genus Chlamydomonas) descended with relatively little change from the ancient algal ancestors of the embryophytes, while within the same division, his class Charophyceae (now known to actually share ancestry with embryophytes) appeared as a dead ended branch. It should be obvious to the reader that Conquest's overall (1960) classification (with a few minor differences) resembles closely that of Eichler (1886) or even some earlier classifications. Like many earlier systems, Conquest did not separate Psilophyta + Calamophyta + Filicophyta from Lepidophyta but placed all these groups within "Pteridophyta" (ferns and fern allies). The main difference in Conquest's system versus many earlier systems was the major division of "plants" into embryophytes and "thallophytes" rather than phanerogams and "crytogams" (traditionally more broadly defined than the "crytogams" of modern ecology). The phanerogams (seed plants) of the older systems correspond to Conquest's division Spermatophyta. The land dwelling bryophytes and fungi (lichens included), as wells as certain land dwelling "algae" together with "bacteria" and all the aquatic "algae," were traditionally lumped together and considered "thallophytes" (including, as a group, the least understood remainder of the "cryptogams"). From Conquest's system, it can be seen that this practice continued well past the middle of the 20th century.

Very few more modern authors may still include all the "algae" in a single subgroup of "plants," but in eliminating the major group called "Thallophyta," they may exclude fungi (traditionally considered plants), lichens (traditionally sometimes confused or grouped with bryophytes), and "fungus-like organisms" (traditionally treated as fungi), as well as most "bacteria" (but often those other than cyanobacteria, which were traditionally treated as "algae"). The less controversial placement within well supported lineages of many of the "terrestrial (land dwelling) algae" [those not considered embryophytes and once haphazardly grouped together with other so-called "thallophytes" (= "nonvascular cryptogams")] has only occurred (more or less) within the last few decades. See also single celled organisms and bacteria names.

Even though lichens have been found to be dual organisms, comprising food producing cyanobacteria or green algae s.s. merged with certain fungi, the lichens are now placed within fungi in groups most closely related to their fungal components. Therefore, with the eventual separation of fungi from the plant kingdom, the lichens are no longer considered a type of bryophyte or "algae".

If (1) "prokaryotes" (mostly unicellular) and (2) "protozoans" or "protists" (mostly unicellular), (3) animals (essentially all multicellular), (4) fungi (mostly multicellular, few unicellular), (5) plants (mostly multicellular and some unicellular), and (6) chromistans (mostly unicellular and some multicellular) are considered six separate kingdoms, the "fungi," if defined from the standpoint of function or ecology, could include heterotrophic "prokaryotes" (e.g., actinomycetes), "protozoans" (e.g., various slime molds), true fungi or eumycotans (e.g., chytrids, microsporidia, yeasts, molds, and mushrooms), and chromistans (e.g., pseudofungi, plasmodiophorids, etc.), while "algae" could include autotrophic "prokaryotes" (e.g., cyanobacteria), "protozoans" (e.g., euglenids), plants (e.g., glaucophytes, "green algae" including "streptophyte algae" s.l., and red algae), and chromistans (e.g., crytophytes, haplophytes, diatoms, chrysophytes, kelps, dinoflagellates, and chlorarachniophytes). In modern ecology, the name "crytogam" is also sometimes used, although more restrictively, for low lying organisms that make up the ground or surface layer of vegetation. For the sake of keeping things as simple as possible, formal and informal names of organisms based on ancestor-descendant relationships (lineages) are emphasized in this work, and names given organisms for other reasons may be included but they are not considered as important for the reader to learn. The formal names not corresponding to lineages are often highlighted and always singled out by placing them in quotes (e.g., the kingdoms "Bacteria" and "Protozoa" of some authors). If informal names not representing lineages have been used over and over again, such as bacteria, prokaryote, protozoan, protist, algae, bryophyte, fern ally, etc., they are not always placed in quotes. Such informal names are often used by many modern authors for organisms with a similar appearance, function, or level of complexity but not necessarily directly related to one another.

According to a few modern authors, all organisms ancestrally with chlorophyll and oxygenic photosynthesis should be considered plants. Although the term has fallen out of favor in recent years, some of these authors still define "Algae" as all plants that lack the characteristics of embryophytes. Other authors exclude cyanobacteria and consider as plants only the eukaryotes that possess plastids. The "Algae" then can be defined as all plants with plastids that lack the characteristics of embryophytes. According to the genes of the plastids all members of this group share a common ancestry with cyanobacteria. They are a monophyletic group with respect to the genes in their plastids. In other words, DNA in the plastids is more closely related to the DNA of free-living cyanobacteria than to the DNA in the nuclei of the cells bearing the plastids. However, according to the genes of the nuclei, the group "Algae" comprises a mixture of unrelated, photosynthetic, usually aquatic eukaryotes. They are a polyphyletic group with respect to the genes in their nuclei. They have become a left-over group of "primitive plant-like organisms" that lack the more derived characteristics of the better understood embryophytes.

Certain photoautotrophic organisms like the mostly unicellular dinoflagellates, although in the past sometimes considered members of "Protista" (or more commonly "Protozoa") but often treated as "algae," are still named according to the Botanical Code (ICBN). Some modern authors, as recent as 2000, still place them in the division of eukaryotes called Dinophyta of the subkingdom "Algae." In such a classification system, "Algae" is defined to include (1) the named divisions of photosynthetic "prokaryotes" called "Cyanophyta" (= cyanobacteria with chlorophyll a) and "Prochlorophyta" (= cyanobacteria with both chlorophylls a and b) plus (2) the named divisions of photosynthetic eukaryotes called Euglenophyta (euglenoids), Chlorarachniophyta (chlorarachniophytes, e.g., the genus Chlorarachnion), Dinophyta (dinoflagellates), Cryptophyta (cryptophytes or cryptomonads), Haptophyta (haptophytes or haptonema organisms), Chrysophyta (chrysophytes or golden algae), Xanthophyta (xanthophytes or yellow-green algae), Bacillariophyta (diatoms), Phaeophyta (phaeophytes or brown algae), Glaucophyta (glaucophytes or glaucocystophytes), Rhodophyta (rhodophytes or red algae), and "Chlorophyta" ("chlorophytes" or "green algae"). Therefore, the photosynthetic subkingdom "Algae" (a narrowed version of the old "Thallophyta") excludes all non-food producing heterotrophs, as well as the chemolithotrophs and anoxygenic photosynthetic bacteria, plus the photosynthetic subkingdom Embryophyta (embryophytes or most land plants).
In such a system of classification, the photosynthetic subkingdom Embryophyta includes the divisions Bryophyta (liverworts, mosses, and hornworts) and Tracheophyta (tracheophytes or vascular plants).
All organisms considered "plants" can still be subdivided as Embryophyta (all photoautotrophs with a well protected embryo) and "Algae" (all left over photoautotrophs, including cyanobacteria, without a well protected embryo).
As recent as the year 2000, such a classification system included the following major groups, all considered part of the plant kingdom:

• Subkingdom "Algae"
  • Division "Cyanophyta"
  • Division "Prochlorophyta"
  • Division Euglenophyta
  • Division Cryptophyta
  • Division Haptophyta
  • Division Chrysophyta
  • Division Xanthophyta
  • Division Bacillariophyta
  • Division Phaeophyta
  • Division Dinophyta
  • Division Chlorarachniophyta
  • Division Glaucophyta
  • Division Rhodophyta
  • Division "Chlorophyta" (including chlorophytes s.s. and "streptophyte green algae" without embryophytes; see viridophytes)
• Subkingdom Embryophyta
  
  • Division Bryophyta (only very recently considered monophyletic)
    
  • Division Tracheophyta (vascular plants)
    
    • Subdivision "Pteridophytina" (only free-sporing vascular plants)
      
    • Subdivision Spermatophytina (seed and pollen bearing vascular plants)

Although the relationships between the divisions of "algae" in the above classification system are not defined in any detail, all the above divisions [with the exception of "Cyanophyta" (= "blue green algae" with exclusion of "prochlorophytes"), "Prochlorophyta" (= "prochlorophytes"), and "Chlorophyta" (= "green algae")] represent valid lineages. Even though "Cyanophyta" plus "Prochlorophyta" probably form a true lineage, "Prochlorophyta" is an artificial group of not directly related organisms within this broader lineage. "Chlorophyta" is paraphyletic only because it excludes its descendant Embryophyta (= embryophytes or land plants). However, even though most of the divisions correspond to lineages, most of these divisions are not directly related to one another. From DNA evidence, the divisions Cryptophyta (= cryptomonads) and Haptophyta (= haptophytes or haptonema organisms) appear nested within a broader lineage recently called Hacrobia (hacrobians). [The super group Hacrobia (= HC) might include haptophytes and cryptomonads, as well as biliphytes, katablepharids, centrohelid heliozoa, and telonemids.] Divisions Chrysophyta (= golden or golden-brown algae), Xanthophyta (= yellow-green algae), Bacillariophyta (= diatoms), and Phaeophyta (= brown algae) appear nested within a broader lineage called stramenopiles (= heterokonts with two dissimilar flagella). Division Dinophyta (= dinoflagellates) appears nested within a broader lineage called the alveolates. Division Chlorarachniophyta (= chlorarachniophytes), including the genus Chlorarachnion, appears nested within a sublineage Cercozoa of the broader lineage called the rhizarians. [The super group Rhizaria might include core cercozoans, such as filose testate amoeba, cercomonads, and chlorarachniophytes, as well as foraminifers, plasmodiophorids, haplosporidians, gromiids, and (early diverging) radiolarians.] The stramenopiles and alveolates appear more closely related to each other than to the rhizarians. The lineage Harosa (= SAR), comprising stramenopiles, alveolates, and rhizarians, may be sister to Hacrobia (hacrobians). These two sister lineages together comprise the expanded lineage Chromista. The lineage Archaeplastida (= Plantae sensu lato), comprising divisions Glaucophyta or Glaucocystophyta (= glaucophytes or glaucocystophytes), Rhodophyta (= red algae), and "Chlorophyta" (= "green algae") + subkingdom Embryophyta, appears sister to the expanded lineage Chromista. The Plantae (glaucophye, rhodophyte, viridophyte) + HC (haptophyte, cryptophyte) + SAR (stramenopile, alveolate, rhizarian) mega group includes the majority of the photosynthetic eukaryotes. Other than the groups of "prokaryotes" representing cyanobacteria, the division Euglenophyta, as the most divergent eukaryotic "algae" (far removed from the plant + HC + SAR mega group), appears to group close to the base of the eukaryote tree of life. From comparison of the genes of nuclei, all the groups of eukaryotes are more closely related to each other than they are to the groups of "prokaryotes" called cyanobacteria. See eukaryotes versus "prokaryotes." As mentioned above, all organisms considered by some authors as "plants" (the groups of subkingdoms "Algae" and Embryophyta) possess chlorophyll and carry out oxygenic photosynthesis. This does not include the photoautotrophic types of "bacteria" that possess bacteriochlorophyll and carry out anoxygenic photosynthesis.

Much of the diversity of life is unknown to most people. Only the larger, multicellular organisms (made up of many cells), such as brown, green, and red seaweeds, fungi, land plants, and animals, are that noticeable. Even though evolution would generally (with notable exceptions) be expected to work from 'lower' (simpler) to 'higher' (more complex) forms of life, the more distinctive or often more conspicuous 'higher' forms are still usually best understood at first by those that study life; and the left over, often simpler forms are often understood later and often defined (at least initially) in terms of what they lack compared to the 'higher' forms. Since multicellular organisms are often more conspicuous, they were often the ones studied first. Consequently, the unicellular organisms initially became the left-over and least understood types. According to Gilbert M. Smith (1938), "the older distinctions between the plant and animal kingdoms (based upon motility, nutrition, and the presence of a cell wall) break down completely when applied to unicellular organisms, and it is quite impossible to establish criteria that will differentiate in a clear-cut manner between" the unicellular ancestor of plants ("protophyta") and unicellular ancestor of animals ("protozoa"). Nevertheless, the fundamental differences between multicellular plants, animals and fungi reflect their independent origins from different unicellular ancestors. Only recently have scientists been able to recognize a likely evolutionary link between certain living unicellular organisms and certain living multicellular organisms that can be considered plants, animals, or fungi. In some cases, the closest living unicellular organisms to the unicellular ancestor of certain multicellular organisms have been likely located. However, this has often required the relatively recent availability of the electron microscope or DNA sequencing. An interesting exception to this is the late 19th century recognition by Haeckel of the unicellular choanoflagellates as the closest living organisms to the unicellular ancestor of the animals. Although not yet certain, it is possible that the closest living relatives to the unicellular ancestor of green plants (Viridiplantae = Chlorobionta = Chloroplastida) may be the mixotrophs (with both photoautotrophic and phagotrophic nutrition) called 'phycomate prasinophytes' (= single cells with large, thick-walled floating stages, or 'phycomata').

Although the construction of the earliest microscopes in the late 17th century by Antonie van Leeuwenhoek led to an initial study of microbial life, our understanding of the importance and vast diversity of these simpler "microorganisms" (often but not always limited to microscopic organisms also called "microbial forms" or "microbes") is still only in the beginning stages, even with important new advances in molecular biology (the study of structure and function of life at the biochemical level of organization, involving, for example, DNA, RNA, and proteins). It has been estimated that fewer than 2% of all microorganisms have been identified. With this small sampling of microbial life, the scientists are now attempting to progress more rapidly in their quest to understand the entire tree of life, which was largely initiated by the comparative study of small subunit ribosomal DNA sequences of a wider selection of known microorganisms. The small unit ribosomal DNA (= mostly, 16S or 18S rDNA) provides the genetic instructions (sequence of nucleotides) for the production (encoding) of small unit ribosomal RNA that plays a role in the small unit of the ribosomes (tiny factory-like subunits of the cell responsible for the manufacturing of proteins). See molecular characters. Recent molecular studies have generally reinforced the older proposals that most of the more complex, conspicuous, and better understood, multicellular organisms can be placed in the kingdoms Animalia, Plantae, and Fungi. However, the separate kingdoms "Monera" (for "bacteria") and the "Protozoa" or "Protista" (for the simpler eukaryotes, including the so-called "unicellular animals") that were first put forward toward the end of the 19th century have largely been discredited, little by little being eliminated from biology textbooks. The "prokaryotic organisms" ("bacteria") once lumped into one kingdom are now considered (by most biologists) to belong to two separate domains, Archaea (= Archaebacteria) and Bacteria (= Eubacteria). The use of the name Bacteria applied to one of these domains may be misleading, because this name has traditionally been applied to the paraphletic group of all "prokaryotes" [including both domains and excluding the domain named Eukarya (= Eukaryota) for all eukaryotes]. Furthermore, if the group named Bacteria (= Eubacteria) is eventually shown to be paraphyletic, it will no longer be considered a legitiment domain, which is suppose to be a primary line of descent (not including organisms of any other domain). Nevertheless, no matter what is finally decided, the concept of the three domains of all cellular life has already become so entrenched among scientists that these names will likely continue to be employed for a long time and, today, can be found in nearly all biology textbooks. The single-celled or simpler eukaryotes, once lumped into a single kingdom, are now known to comprise diverse groups not that closely related to one another. It was already recognized before the last half of the 20th century that the subgroup "Mastigophora" (~= "Flagellatae," often unicellular organisms called "flagellates," possessing flagella = tiny whip-like or hair-like extensions propelling the cells) consists of a polyphyletic assemblage of unrelated "protozoan" or "protistan" life forms. The same was eventually said for the subgroups once called "Sarcodina" [the "amoebas" = often single-celled (unicellular) organisms with a soft, gelatinous cell surface that can become extended as pseudopodia ("false feet"), which enable them to move about and capture (engulf) prey] and "Sporozoa" [often unicellular parasites forming a protective spore to get from one host organism to another]. Such "flagellates" or "amoebas" or "sporozoans" are now thought to be found in scattered clusters (unrelated groups) on both the so-called animal and plant side of the tree of life for all living neozoan eukaryotes.
The old classical system of grouping "Protozoa" (more or less abandoned decades ago) was largely based on the work of Butschli (1880-1889), defining four major groups as "Sarcodina" (= "amoeba type organisms"), "Sporozoa" (~= "unicellular parasites"), "Mastigophora" (= "flagellates"), and Infusoria (= ciliates).
The last major subgroup (the only group now recognized as a true lineage) of the old kingdom of "protozoans" was called Infusoria (= Ciliophora, the ciliates, including the familiar Paramecium). This subgroup of heterotrophs (not food producers, depending on other organisms for food) is now thought to be localized on the plant side of the tree for all living neozoan eukaryotes and placed within the larger group of alveolates, those organsms with a pellicle (a body covering within the cells that is more complex than just the surrounding plasma membrane); and the (peripheral but somewhat under the cell surface) pellicle is composed of distinctive, flattened, sac-like structures called alveoli, sometimes giving the cells a pitted or honeycombed appearance. Another group of organisms within the alveolates, are the Apicomplexa (including among others the malaria parasite) and mostly photoautrophic organisms (traditionally considered "algae" or "protozoa") called the dinoflagellates, many of which form plates of cellulose and other rigid materials surrounding the alveoli, therefore, developing a somewhat internalized cell wall.

Since it is doubtful whether viruses are alive, the cell is the basic or smallest unit that makes life possible. On the basis of cell structure, Chatton (1937) divided all cellular life into two categories, eukaryotes versus "prokaryotes." The eukaryotes were defined as those organisms whose cells consisted of a double membrane bound nucleus (now known to contain most of the units of inheritance called genes located on often thin, often elongated structures called chromosomes) and certain other, membrane bound organelles (distinct 'organ-like' components or structures within cells that perform specific functions), while "prokaryotes" lacked these features. The cells of "prokaryotes" (the "left overs") were again (artificially) defined by their relative structural simplicity, and by the absence of many features found in the cells of eukaryotes. Some authorities restricted the definition of organelles to membrane bound structures within the cells that have a particular function, while others defined these functional structures more broadly. Therefore, the term 'organelle' can more generally apply to subcellular (within the cell) structures of both "prokaryotes" and eukaryotes; some of these structures (e.g., the centers of protein manufactor called ribosomes) in both groups can lack bounding membranes; but those organelles with one or more bounding membranes (other than the universal 'envelope' called the plasma membrane that surrounds the entire cell) are unique to eukaryotes and, therefore, absent in "prokaryotes." All these membranes (including the plasma membrane) are very thin, two layered films of fats (more specifically called phospholipids) with inserted proteins and sometimes other substances. However, there are inner membranes unique to eukaryotes, including those surrounding certain organelles, that are not derived from the plasma membrane but can often interact closely with it. Although some "prokaryotes" can possess internal membranes derived from their plasma membrane, these internal membranes are never found to surround organalles. Conventionally, the plasma or outer membrane is considered the boundary of all living cells, although most cells produce and secrete materials of one kind or another that make up a surrounding cell wall or an extracellular (outside the cell) matrix. Even though this material is conventionally considered to reside outside the cell, the study of these outer structures is central to any understanding of the cell because they are an integral part of cell functions. In eukaryotes, the internal membranes (unlike those of certain "prokaryotes") can be considered extensions of the membrane system that bounds the nucleus. Actually, the separation of eukaryotes from all other "left-over" life forms based on these somewhat cryptic (microscopic) differences was first suggested by Chatton (1925). The formal name for eukaryotes is still largely accepted as Eukaryota Chatton, 1925. Note that the date of publication by the author can be optionally included as part of the name.
Although the distinction between eukaryotes and "prokaryotes" had already much earlier been made by Cohn (1875) (see single celled organisms) and more recently on the basis of internal cell structure by Chatton (1937), it took some time for Chatton's work to be generally accepted, possibly partly due to the reluctance of botanist (plant scientists) and phycologists (scientists that study "algae") to remove cyanobacteria (formerly called 'blue green algae') from their classification systems. It should be noted that there was never any major separation of eukaryotes from "prokaryotes" in the old two or three kingdom systems of classification, which largely applied only to multicellular organisms. It was mostly through publications of Stanier and co-workers (e.g., Stanier and van Niel, 1962; Stanier et al., 1963) that the eukaryote versus "prokaryote" distinction became widely acknowledged. The living material bounded by the plasma membrane of both "prokaryotes" and eukaryotes is now called protoplasm. In eukaryotes, the protoplasm other than in the membrane bound nucleus is called cytoplasm. All the organelles, including the usually centrally located nucleus and its internal membrane extensions, can be thought of as embedded in the cytoplasm. See short descriptions of the universal plasma membrane and internal membranes with an emphasis on fungi (a type of eukaryote).
The cells of "prokaryotes" (including eubacteria and archaea) are limited to a few compartments, such as the plasma membrane, the cell wall (gram-positive eubacteria and archaea), the periplasm, and the outer membrane (gram-negative eubacteria), while the cells of eukaryotes feature numerous compartments (see last common ancestor), including the endoplasmic reticulum (ER), and the Golgi apparatus (see internal membranes), the tiny membrane bound sacs called vesicles and lysozomes that contain digestive enzymes, the larger membrane bound sacs called vacuoles, the plasma membrane, sometimes a cell wall, and the various organelles, such as the nucleus, plant chloroplasts, mitochondria, and peroxisomes, as well as sometimes even more internal compartments within certain organelles that can be surrounded by one or a few (2 or 3) outer membranes.

In attepting to define what is usually meant by "microrganisms" versus "macroorganisms", those once formal or even informal group names with quotes represent artificial groups containing organisms that are not directly related. The group names whether formal or informal without quotes can be considered monophyletic or true lineages. The placement of what was eventually (1930s and 1940s) considered a separate kingdom "Monera" ("prokaryotes" or "bacteria") as a class of "plants" persisted into the twentieth century. Physicians still use the phrase "gut flora" for the microbes of the human GI tract. While "fungus-like organisms" and true fungi, as well as some "protists" and many "prokaryotes", were once considered plants and included (as some of the often less understood "left-overs") in botany or some "protozoa" were once considered animals and included (as often less understood "left-overs") in zoology, all these organisms (even the larger ones) are now often included in microbiology and considered "microrganisms" or "microbes" [i.e., all the "left-over" organisms (mostly but not necessarily microscopic) that are now not considered plants or animals]. These are the less conspicuous and less understood organisms (mostly microscopic) that would have been placed among the "cryptogams" or the so-called "unicellular animals" based on the old two kingdom classification of life. Some of these organisms are the ones that were once placed in traditional groups that are now largely considered paraphyletic or polyphyletic. The names of some of these traditional but artificial groups are still often employed only for convenience as "catch-all" categories in the study of superficially similar but often not directly related organisms. Although the majority of what are today called "microorganisms" (= "micro-organisms") include a diverse group of microscopic organisms that mostly exist as single cells or cell clusters, they are not limited to microscopic single cells (or cell clusters) or even cellular forms, because they have come to include microscopic but noncellular viruses, the mostly microscopic and always cellular "prokaryotes," and the larger cells of the eukaryotes often called "Protista" or "protists" [= "algae" plus "protozoa" (organisms sometimes called "protozoans"), as well as "fungus-like organisms"]. The "Protista" (= "protists"), including the "microbial eukaryotes" that are neither land plants, animals, nor true fungi, is considered an artificial group that includes (among others) organisms as diverse as green algae, red algae, glaucophyes, foraminiferans, chlorarachniophytes, radiolarians, oomycetes, brown algae, diatoms, golden algae, dinoflagellates, ciliates, apicomplexans, parabasalids, diplomonads, kinetoplastids, euglenids, cellular slime molds, plasmodial slime molds, entamoebas, and gymnamoebas. These have become the approximate "left-overs" of the three kingdom system of life. Therefore, even through they are not limited only to unicellular or microscopic organisms (some eubacteria can grow to macroscopic size and some "algae" and true fungi can cover hectares), the "microorganisms" (the modern, often less understood, approximate "left-overs" of the two kingdom system of life) are distinguished from the cells of the "macroorganisms" (= "macro-organisms"), which include those better understood, multicellular organisms considered animals and the land plants (or their aquatic embryophyte descendants). In other words, even though most of the "microorganisms" included in microbiology are microscopic organisms with single cells that can carry on life processes of growth, energy generation, and reproduction independently of other (alike or different) cell types, this area of study also includes some larger unicellular or multicellular organisms that are not considered plants or animals. Furthermore, not only are the majority of the organisms on this planet, including most eukaryotes, now considered "microorganisms" (or "microbes"), but also some of the multicellular eukaryotes now considered "microorganisms" (e.g., certain fungi comprising a huge, underground network called a mycelium of simple filaments of cells that produces the surface growing fruiting bodies called mushrooms) are among the largest life forms on the planet. Among the "protistan eukaryotes" (or "protists"), the unicellular or multicellular, phototrophic "algae" include organisms mostly with cell walls and almost always with chlorophyll containing chloroplasts, while the unicellular "protozoa" are mostly phagotrophic (= phagocytic) and mostly without cell walls, always nonphototrophic without chlorophyll containing chloroplasts (except for the enigmatic microscopic organisms with both "animal-like" and "plant-like" features, such as euglenids and chlorarachnophytes, that are also considered "algae"), usually colorless and motile [except for the sporozoans (Apicomplexa or Sporozoa) that are nonmotile and parasitic], often with motility structures called cilia (Ciliophora) or flagella ("Mastigophora") or amoeboid ("Sarcodina" or "Amoebae") with streaming of cytoplasm resulting in pseudopodia, and never aggregating (like in "slime molds") to form fruiting bodies or masses of protoplasm. The euglenids can be considered both "algae" and "mastigophorans" ("flagellated protozoans"), because in darkness they can spontaneously lose their chloroplasts and become completely heterotrophic organisms. This is not surprising, since euglenids are actually closely related to the flagellated protozoan Trypanosoma, a parasitic genus (thus completely heterotrophic) that includes species that can cause a number of diseases in vertebrate animals, including African sleeping sickness in humans. The dinoflagellates are also often considered both "algae" and "flagellated protozoa" with a close relationship to Apicomplexa and Ciliophora. The "fungus-like organisms" include among others the "slime molds" that lack cell walls (similar to "protozoa") but that aggregate to form fruiting bodies (cellular slime molds) or masses of protoplasm (acellular slime molds).

Although the succession of many other ancestral events must be explained to get a fuller understanding of the plants called trees and in turn the flowers, fruits, and seeds of the herbs, shrubs, and trees of flowering plants (angiosperms), these were (from the standpoint of the human history of western botany) some of the first more conspicuous plants or plant parts to be recognized and studied. However, in order to truly understand trees, and the flowers, fruits, and seeds of the herbs, shrubs, and trees of angiosperms, a bio-historic perspective (from the standpoint of biological evolution) is necessary, concentrating on the descent with modification that led to the simplest, historically (from the standpoint of the history of botany) least understood land plants and their "streptophyte green algae" relatives, which are descendants from earlier forms of life that were often even less understood. This step by step descent with modification started about 4 billion years ago with very simple life forms and has culminated in the dominance of angiosperms from the Cretaceous to the present (see also early fossils). In order to really understand plants, this bio-historical perspective is necessary. Without it, structures like chloroplasts, woody trees, seeds, and fruits or processes like the land plant life cycle make no sense whatsoever. In the description of the wide diversity of medicinal organisms featured in this work, this is the perspective that is emphasized. However, from the standpoint of the history of botany, the more recently derived, often more conspicuous organisms were the first to be recognized and studied, more or less leaving for the last the study of the often less conspicuous descendants of the more ancient, often simpler forms of life. It was not until around 1840 and soon after that studies with the help of the microscope on plant sexuality and embryology was no longer confined to the phanerogams (seed plants) but was extended to the higher and later on to the lower "cryptogams" ("non-seed plants"). In the year 1850, comparative studies by Hofmeister of the formation of the embryo and alternation of generations in phanerogams, "vascular cryptogams" (= "pteridophytes" = ferns and "fern allies"), and mosses were beginning to unravel the true nature of the seed. However, the true nature of the lower "cryptogams" once called the "thallophytes" (including "algae," "fungi," "bacteria," etc.) were the last to be recognised. By 1852, systematic relations between past and existing floras, established through the comparative study of the fossils and living plants by Unger, showed that the immutability of species is an illusion. However, it was not until the revolution in biology started by Charles Darwin that the bio-historic perspective eventually became basic to taxonomy. According to Kevin de Queiroz (1997), the next stage in this revolution will probably involve the extention of the central role of descent with modification into the realm of biological nomenclature (the scientific naming of living and fossilized organisms and their lineages).

Much confusion in names (the same name for different organisms or different names for the same organisms) has often resulted from attempts by authorities to define ranks for the plants that they are trying to classify, especially when the kingdoms are defined differently from one author to the next. For example, some literature sources might define Plantae Haeckel, 1866 as the questionable lineage (also called Archaeplastida), including all the purported descendants of the first eukaryote with oxygenic photosynthesis, while other sources may apply Plantae (with the same author and publication date of the name) to only the land plants. The use of qualifiers, such as sensu lato versus sensu stricto may be used to distinguish these two applications of the same name. The first could be called Plantae sensu lato, while the second could be called Plantae sensu stricto. The same name Chlorophyta can also apply to different groups, such as all green plants (a lineage), "green algae" (a grade), or only (as above) a lineage portion of the "green algae" grade. The name Charophyta includes (as above) all organisms that can be referred to as streptophytes sensu lato or only the group of streptophytes sensu stricto in the order Charales, thought by some but not all authorities to be likely most closely related to green land plants.

However, the problems with ranks can be mostly seen as the result of the tremendous progress in identifying the major lineages of organisms within the last few decades. Because of this progress, a particular formally named lineage may be placed within so many larger lineages, each requiring a formal name, that not enough ranks or taxonomic levels exist to easily label this hierarchy. Therefore, this problem is very simple. There are more nested sets of lineages now known than can be easily accommodated by the traditional species to kingdom hierarchy.

Take for an example the group organisms referred to as Achillea millefolium L. (= Yarrow), a species that is a member of the genus Achillea L., which is part of the Eurasian grade of the tribe Anthemideae; and this species can be found wild not only in Europe, Asia, and North Africa, but also in western North America and Mexico.

If all known major lineages that contain Achillea millefolium up to the domain Eukaryota (= Eukarya) are listed, this species would have to be grouped in a nested hierarchy including Achillea (genus), Matricariinae (subtribe), Anthemideae (tribe), Asterodae (supertribe), Asteroideae (subfamily), Asteraceae (family), Asterales (order), Apiidae, Campanulidae, Gentianidae, Asteridae, Pentapetalae, Gunneridae, Eudicotyledoneae, Mesangiospermae, Angiospermae (flowering plants), Spermatophyta (seed plants), Lignophyta, Euphyllophyta, Tracheophyta (vascular plants), Embryophyta (embryophytes, commonly called land plants), Streptophyta, and Chloroplastida [= Viridiplantae].

In turn, Chloroplastida might (?) be nested within Archaeplastida, which seems (?) to be nested in an informally named lineage sometimes referred to as cordicates, which has recently been proposed to be nested within the group now called the neozoans within the group of neokaryotes (the "core excavates" plus the neozoans) within the domain or superkindom Eukaryota. This hierarchy is almost certain to be correct up to and possibly somewhat beyond the level of Chloroplastida; and it would, of course, be useless to attempt to show that Achillea millefolium is not a member of the monophyletic domain Eukaryota.

However, at the level of the domain Eukaryota, if all the known lineages are named, it would be very cumbersome to try to fit or accommodate Achillea millefolium along with other organisms into a traditional hierarchy that permits a limited number of conventional ranks. Almost any of the names of the known lineages above the rank of order would have to be changed to a name with an appropriate suffix; some unconventional intermediate ranks (e.g., supersubdivision) could be used; or more than one classification system could be employed, one or more for the higher ranks and another for the lower ranks. For example, in one classification system, Archaeplastida could be considered the kingdom in an attempt to accommodate some of the higher level names down to and including the name for embryophytes. In another (separate) classification system, Chlorobionta could be considered the kingdom in an attempt to accommodate names for many of the higher level lineages of "green algae" in relationship to embryophytes. In still another (separate) classification system, the embryophytes could be considered the kingdom in an attempt to accommodate many of the lower levels, including all the classes, orders, and families of ferns and the classes of seed plants. In a final classification, the names ranked as classes of seed plants of the last mentioned system could, perhaps, be ranked as supersubdivisions (or some other unconventional intermediate rank) of the division Spermatophyta. Although some of the same lineages are included in these different classification systems, the change in rank requires different names for the sames lineages in one classification system versus another. The creation of different names for the same lineages violates the principal of having only one name for any group of organisms that descend from a single common ancestor.

Somewhat of the same problem exists for the classification up to eukaryotes for our species:
Homo sapiens (species), Homo (genus), Homininae (subfamily), Hominidae (family), Hominoidea (superfamily), Catarrhini (parvorder), Simiiformes (infraorder), Haplorhini (suborder), Primates (order), Euarchonta, Euarchontoglires (superorder), Boreoeutheria, Eutheria (infraclass), Theria (subclass), Mammalia (class), Amniota, Tetrapoda, Dipnotetramorpha, Sarcopterygii (bony fish and descendants), Teleostomi (bony vertebrates), Gnathostomata (jawed vertebrates), Vertebrata, Craniata (subphylum), Chordata (phylum), Deuterostomia, Bilateria, Eumetazoa, Metazoa, Opisthokonta (kingdom), and Eukaryota (domain or superkindom).

Even though classification systems that 'reflect' well supported relationships between true lineages can sometimes be based on a hierarchical structure of ranks, such systems of names tend to be awkward and difficult to construct. Nevertheless, these so-called rank-based phylogenetic classifications are still in common use. See working classification of "green algae" and land plants by Lewis and Mc Court (2004). However, because of various problems and limitations of the traditional species to kingdom hierarchical systems, a recent trend in systematics permits (although this does not require) the abandonment of ranks. This allows ranks to be optional so that the system of names can be more consistent with a binary tree-like hierarchical structure of relationships between organisms based on lineages and sister groups. Uses of informal unranked plant names above the level of order have become common. However, care most be taken to avoid applying the same informal name for more than one lineage. The ranking of groups in a species to kingdom hierarchy can be arbitrary and include some of the most subjective aspect of traditional taxonomy. The changing of the ranks and, therefore, the names (= name changes due to shifts in rank) can lead to far too many names for the same lineages. There should be a way to easily name lineages (even as they are being discovered) one at a time (just like naming species) without the worry of fitting them into a new or preexisting rank based classification. Because of the potential problems or limitations with mandatory rank based systems, a multitude of newly uncovered and well-supported lineages would often be left unnamed, causing taxonomy to lag far behind knowledge of genealogy. Therefore, the divorcing of naming from ranking is especially needed at a time when advances in molecular biology and computer technology are rapidly generating so much new information about the relatedness of organisms. This fortunately does not mean that every lineage in a branching and rebranching genealogy must be named. However, those that are named should be not only well supported as monophyletic groups but should also be at least easily recognizable. Furthermore, the names of well-supported lineages that are also well established in the literature should be preserved. Name changes should be minimized as much as possible. Although (in compliance with the standards of ICBN) there is an attempt to use (as much as possible) the oldest standard names that apply to well defined lineages, especially at or below the traditional rank of class or order, none of the various names applying to the ranks themselves of traditional classification systems of various authors are emphasized in this dictionary, which stresses the grouping of organisms and the naming of groups based genealogy.

Hierarchical structure of levels (similar in some ways to the systematic arrangement attributed to Carl Linnaeus) is still more or less used today. However, classification of living organisms is often based (as much as possible) on a tree-like diagram representing genealogy that is reconstructed using more refined methods than those solely based on overall similarity of characters (see phenetics versus cladistics). Although sometimes yielding apparently favorable results in grouping plants or other organisms with distinctive characteristics, overall similarity methods have often failed to provide reasonably accurate estimates of genealogy. Currently, there is an emphasis on isolating distinctive features that share a common ancestry (referred to as shared divergent or derived characters) in defining lineages and sister groups. This can be thought of as the grouping of living things on the basis of shared changes from ancestrally less derived to more derived or divergent conditions due to evolution. Therefore, the branching pattern of a genealogical tree (estimated on the basis of uniquely shared changes from certain ancestral features) can be thought as due to divergence from ancestors to descendants, also referred to as diversification or evolution (descent with modification). See some simple example.

Genealogy (= phylogeny) can be defined as the study of the descent with modification of living organisms from earlier ancestral forms or the (natural evolutionary) relationships of these organisms proposed on this basis and often represented by a tree-like diagram called a genealogical tree. There is much effort today in biology (the study of life) to eventually represent all the diversity of life as a single (very large) genealogical tree called the tree of life. This diversity of organisms comes about through a process referred to as diversification or evolution (descent with modification of certain characteristics). All organisms, living and extinct, fall into systematic arrangement, an orderly series of successively larger and larger groups subordinated to each other on the basis of similarity (particularly shared divergent characteristics). That the diversity of life is not a set of completely unique organisms but a nested hierarchy of lineages of organisms that share divergent similarities is probably the most convencing support for biological evolution. The evolutionary perspective is now generally becoming the most important approach to plant description, identification, classification, and even plant naming. However, this genealogical approach has only gradually developed in the last few decades (since the 1960s) from earlier refinements of the concept of biological evolution first introduced by Charles Darwin (1859) in The Origin of Species. Even though the objectives of the fathers of traditional taxonomy had nothing to do with any concept of biological evolution, they (by placing all known organisms into a logical classification, which was often believed would reveal the great plan used by the Creator - the Systema Naturae), laid the framework for later evolutionary schemes by dividing organisms into a hierarchic series of taxonomic categories, starting with kingdom and progressing down through phylum, class, order, family and genus to species. In the 18th and early 19th centuries, naturalists likened this hierarchic series to a 'tree of life,' a notion that was adopted by Charles Darwin as a means of describing the 'branching' evolutionary histories of all known living organisms (including fossils).

Although closely related organisms have overall more similarities in their characters than more distantly related ones, it is important to distinguish primitive or less derived characters from those that are more advanced, divergent, or derived and establish groups at different levels of the hierarchy on the basis of shared derived characters with a common ancestry (an approach to grouping organisms already mentioned but discussed in more detail below). What is considered a divergent (advanced) character at one level can be considered an ancestral (primitive) character at a higher level on the tree of life. Therefore, both divergent and ancestral characters are actually included in the reconstruction of the evolutionary history of organisms represented by a genealogical tree; and it depends on the level of the hierarchy whether a given character is divergent or ancestral.
An example of such a hierarchy of groups in animals could be humans (e.g., with language able to express symbolic thought, fire used in cooking food), primates [e.g., with grasping hands or feet, often composed of a few opposable digits with skin ridges allowing for finger or toe prints, flattened finger or toe nails (not narrow claws), forward-facing eyes close together on front of face allowing for binocular and stereoscopic vision, relatively large brains, short jaws, flat faces, and extended parental care of offspring compared to other mammals], mammals (e.g., with hair and milk secreting glands, differentiation of teeth (= different types, such as canines, molars, etc., not all conical or uniform in size and shape)], amniotes [e.g., animals bearing complex eggs with internal membrane bound compartments, including the membrane bound amnion with an internalized pond-like fluid surrounding the embryo that develops from cell division of zygote (= fertilized egg cell, ovum, or female gamete)], tetrapods [e.g., with four limbs or legs with digits, pharyngeal clefts (grooves along sides of pharynx) giving rise to parts of ears, glands, etc. (never giving rise to gill slits as in other vertebrates), ears able to detect airborne sounds], vertebrates [e.g., with series of vertebrae of cartilage or bone, comprising a backbone], etc.
A common hierarchy for plants could be flowering plants or angiosperms [e.g., with true flowers that bear fruit], seed plants [e.g., with seeds], vascular plants [e.g., with well developed water and food conducting tissue], polysporangiophytes [e.g., sporophyte with branches bearing multiple spore sacs], embryophytes also commonly called land plants [e.g., with distintive embryo (developing from cell division via mitosis of zygote (fertilized egg cell)) that is at least initially attached to (dependent on and often nourished by) a gametophyte and enclosed within a protective structure (sex organ or seed)], phragmoplastophytes [= land plants plus closest (presently living, water inhabiting) "streptophyte green algae" relatives of the land plant ancestor that have cell division involving a distinctive (often cigar-shaped) structure (between the seperated nuclei of the dividing cells) called the phragmoplast composed of minute tubules (microtubules made of the proteins called alpha and beta tubulin) associated with minute, membrane bound (sac-like) structures called vesicles], etc.
At least one shared divergent character in brackets in the prior sentences for animals and plants is used to help define each named lineage (composed of a single ancestral species and all its descendants), starting (in a hierarchy) from the least inclusive groups and ending with the more inclusive ones. In using this dictionary, it would be helpful to learn the important characteristics that can be used to define these major levels of the plant hierarchy, as well as the higher level lineages for vascular plants (lycophytes and euphyllophytes). Each shared derived character, when unique to a particular lineage or branch of descent, can be considered a character that can serve as a marker (shared change) useful for identification of this lineage. The major branches of the so-called tree of life can be referred to as higher level lineages often supported by recent DNA evidence (as well as often distinctive morphological characters of form and structure). See more on what is meant by lineages and sister groups in the next paragraph.

Lineages and sister groups

A lineage can be defined as a group that must include a single ancestral species or most recent common ancestor (MRCA) and all its descendants. These descendants may also include lineages [often represented as branches (of descent) in a tree-like diagram (a genealogical tree)], but they must all be branches that stem directly or indirectly from the same common ancestor. According to Doyle & Donoghue (1993), a crown group (= grown lineage) includes the MRCA of the presently living members of a lineage (= clade) and all its descendants (= derivatives) and not the fossil members of the stem groups (= stem relatives, stem lineages, or stem clades) that gave rise to the crown group or lineage. Although genealogical (phylogenetic) tree-like diagrams always represent an oversimplification, their branching, hierarchical structure (= topology) provides just enough information to make it much easier to understand the evolutionary history of organisms. Therefore, the structure of these tree-like diagrams is commonly used to illustrate the nature of lineages as apposed to "artificial groups" that are either paraphyletic or polyphyletic. In these diagrams, each labeled tip, which could respresent a species, genus, family, order, class, division, kingdom, or even domain, is called a taxon (plural: taxa); the internal nodes represent the most recent common ancestor of a given collection (group) of descendant taxa; the root node represents the MRCA of all the taxa of the tree; the root branch (or root) and the branches that connect the taxa, internal nodes, and root node can represent evolution or shared divergent changes in the states of characters over time; the nodes also represents the points at which common ancestors split (diverge or bifurcate) along at least two branches; and the external branches directly connect each terminal taxa to its MRCA, while the internal branches connect the internal nodes to other internal nodes or the root node. The nodes can be considered taxa only if they represent particular named ancestral organisms, such as specific known fossils. The most important aspects of the structure of such a tree are the order of branching (representing evolutionary history of the taxa) and the groupings of taxa by their MRCA (representing lineages or clades). If such a tree is represented vertically, it is called a vertical tree, where the root is often located at the bottom and taxa are the tips at the top (such a tree can also be represented up-side-down with the relationships of organisms uneffected). In such a tree, the left-to-right order of the labeled tips has no meaning, because the subtrees at the internal nodes or the entire tree at the root node can be freely rotated (spun at the nodes), thereby reversing this order. The tree after any such possible rotation is considered identical (in meaning in terms of evolutionary history) to the prior tree. The rotation of the entire vertical tree 90 degrees results in a horizontal tree, with no effect on the branching order of the nodes and taxa or the groupings of taxa by their MRCAs. The vertical axis (y-axis) of the vertical tree or horizonal axis (x-axis) of the horizonal tree represents time from the past to the present. The points on these axes can be used to estimate the time of the past splitting of the root node, internal nodes, and external nodes, leading terminally to the present taxa. The resulting groupings in these trees are said to be monophyletic, if and only if each of these groupings includes nothing else except a single node and all the descendants of this node. A lineage (= clade) is always a monophyletic group.

E   A   B
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   \ /
    -
    | root

In order to define lineages on the basis of characters used to describe them, there is a need to focus on the changes or divergences from corresponding ancestral conditions. This can be thought of as the grouping of living things on the basis of shared changes (from ancestral to divergent or derived conditions) due to biological evolution. Homologous characters (features with a common ancestry) can be represented by a change from a primitive (often simpler) state to a more advanced or derived (often more elaborate) state. These differences, due to changes with a common ancestry, represent two or more states of the same character; thus, they are called character states, which can, for example, be coded 0,1 or 0,1,2,3, where the lower numbers usually represent more primitive (ancestral) states and the higher numbers more advanced or derived states. If character states are represented by only 0 or 1, this is called binary coding. The successive increase in these numbers can be thought of as steps in evolution. The multi-state characters (those with more than two states) are often treated as unordered (no assumptions are made about whether any of the states are more or less derived than any other) and the steps of evolution are estimated by the methods used to analyze this coded information, often represented by a two-dimensional matrix of names of organisms versus their characters (each represented by a particular coded character state). Sometimes all character states (binary or multi-state) are treated as unordered. Molecular characters, for example, from the DNA sequences of genes can be coded as A, C, G, or T, representing the abbreviations of their individual (sequential) building blocks or subunits called nucleotides. A DNA sequence for a gene, for example, can be coded as a sequence of these letters representing its substituent nucleotides. Despite which type of characters is employed in uncovering evolutionary relationships of organisms, the shared derived character states (not the ancestral conditions prior to the changes) are used (whenever possible) to help define the lineages.
In defining lineages on the basis of changes in shared characters from ancestral to more derived states, one qualification should at least be mentioned. If lineages are to be defined on the basis of shared changes, it is also important to note whether the change occurred at the beginning of a lineage or sometime after the lineage arose and only in a portion of its members. This is not always easy to determine (especially when the only living members possess the change that occurred after the lineage originated), but sometimes the characters of fossils can provide useful reference points. An ancestral condition refers to a feature or character of the ancestor of a group or it may be a homologous condition (related by descent) that existed prior to the origin of the group. The ancestral state of a particular character of a lineage is the state possessed by the ancestor of the lineage; it is, therefore, said to be ancestral to the lineage. Such a state may be modified (become a more derived state) later within a lineage. In this case, it is the ancestral state that applies to the entire lineage, because the modified state applies to a change that took place later in only a portion of the lineage. Consequently, the modified state can only be used to distinguish a portion of the lineage and does not apply to the entire lineage. This distinction is important, because apparently similar derived characters can arise multiple times within sometimes unrelated lineages. Therefore, it is often helpful to determine whether a derived character change has occurred at the very beginning of a lineage or somewhere within the lineage. This is why the characters of fossils are often important in understanding the lineages of modern organisms.
By taking into consideration the above qualification, the following simple examples of the grouping of organisms on the basis of a few shared changes should shed a little more light on this subject. If aquatic (water inhabiting) relatives called "streptophyte algae" led to land inhabiting embryophytes, the lineage of embryophytes can be defined by some shared unique character (e.g., the distinctive protected embryo), found in all embryophytes but not in the "streptophyte algae". The so-called "non-embryo producing plants" (most "algae"), "non-vascular land plants" [bryophytes (liverworts, mosses, and hornworts) + some polysporangiophytes without well developed vascular or water and food conducting tissue], "non-seed vascular plants" (any vascular plant with water and food conducting tissue and without seeds), and "non-flowering seed plants" (any seed plant without the parts of fruits called carpels) are defined by the absence of one or more changes; and, therefore, they may not be lineages, because they often represent mostly the ancestral condition before the changes took place. Plants in these often "non-lineage" groups (often considered as grades) will sometimes be featured together to help contrast the ancestral condition from the changes that took place in true lineages, but it is the lineages that help to accurately pinpoint the nature of a particular type of plant. Sometimes so-called non-group name can represent a lineage (e.g., living non-lycophyte vascular plants for the euphyllophytes), if this group can be defined by shared changes with a common ancestry. In this case, before lycophytes (today represented by club mosses, spike mosses, and quill worts) and euphyllophytes (today represented by ferns, horsetails, and seed and flowering plants) became separate sister lineages, the ancestor of both groups had dichotomous branching (branches successively forked in groups of two with no single main stem). This ancestral condition was retained in all of the earliest lycophytes (a group that was ancestrally with dichotomous branching) and was only modified later within this lineage. However, the earliest euphyllophytes already represented a change from dichotomous branching to overtopping (ancestrally with one long main stem and shorter side branches). In the ancestor of both lycophytes and euphyllophytes, the spore sacs were located at the tips of dichotomous branches. Although euphyllophytes did not have dichotomous branches (except those apical branchlets called terminal trusses), the earliest members of this group retained the ancestral terminal spore sacs (on the tips of the branchlets). This ancestral condition was only modified later within the lineage. However, the earliest lycophytes already represented a change from terminal spore sacs to lateral ones (those arising from the sides of branches). Therefore, the lineage of lycophytes can be characterized by lateral spore sacs, while the lineage of euphyllophytes are ancestrally distinguished by overtopping of branches. The definition of these two lineages is not based on the presence of the most primitive character states (e.g., dichotomous branching or terminal spore sacs). All presently living non-flowering seed plants and the flowering plants also appear (on the basis of DNA evidence) to be sister lineages. However, it is presently difficult to find a single, easily observable shared, derived character state that distinguishes presently living non-flowering seed plants from all other lineages, including true flowering plants; and non-flowering seed plant fossils may eventually be identified that represent an ancestral line from which true flowering plants have originated.

Taxa (singular: taxon) are named taxonomic groups (= taxonomic units), often ranked as species, tribes, families, orders, classes, phyla or divisions. Today, a taxon is ideally a named group of organisms that is monophyletic. Often a plant or group of plants can be diagnosed or identified as a mixture of primitive (retained) characters (that have not changed) in addition to derived characters (that have changed) from the ancestral condition. Therefore, for the purposes of identification of plants or other organisms by using keys, a mixture of diagnostic primitive and derived characters can be employed. However, although not all traditional taxa are always true lineages, it is more and more recommended in modern taxonomy that all taxa should be strictly redefined according to shared derived (homologous) character states; and this can be done, as long as they represent true lineages, without always the need for a strict definition of rank or taxonomic (hierarchical) level. Furthermore, in the sometimes ranked classification systems based on lineages, a certain class may be the sister group to a higher ranking subdivision of other classes, but the first mentioned class may have no defined subdivision or the class itself may be considered the same as its subdivision. Therefore, in order to ensure that a plant gets placed in a lineage, it should always (irrespective of considerations of rank) be grouped with other plants only on the basis of shared derived (advanced) characters, never on the basis of the shared retained (primitive) characters, and ranking is only optional (not strictly enforced, according to the rules of traditional classification). One major reason why overall similarity methods often do not work very well is because these methods group plants on the basis of all shared characters [including not only derived (advanced) but also retained (primitive) ones]. The derivation of genealogical relationships (often simply called genealogy) within or between lineages is effectively done only by grouping plants on the basis of shared changes from related ancestral conditions. However, problems can also result from grouping on the basis of overall similarity of derived or divergent character changes, because the derived character changes may arise from different ancestral conditions (from different, unrelated origins). Each type of derived character change must represent homologous character states (that arise from a corresponding and related ancestral condition); and this type of derived character change must not be considered the same as one that only appears similar (a look-alike) but is the result of changes that are nonhomologous (from different unrelated ancestral conditions). If characters of shared changes from corresponding (related) ancestral conditions are easily recognized, these diagnostic characters can help in placing a plant in its appropriate lineage, and the identification of this plant becomes greatly simplified. The less reliable overall similarity methods are now called phenetic (or distance) methods, while the more reliable grouping of organisms based on shared changes from corresponding ancestral conditions is referred to as cladistic (or shared, derived character) methods. Of course, the responsibility of doing all this correctly or reliably is not completely left to the readers. They are introduced to diagnostic characters based on the labors and consensus of various authorities. Familiarity with often simple diagnostic characters of lineages (shared changes from corresponding ancestral conditions used to define lineages) becomes basic to proper plant identification. Therefore, before more detail is covered elsewhere, the reader is provided information on some of the basic defining features for the major land plant groups.

The lineages are often given special names (informal or formal) to emphasize their importance (e.g., polysporangiophytes for those that first had dichotomous branching, representing a change from an unbranched, spore bearing, land plant with a single spore sac to a branched, spore bearing land plant with multiple spore sacs). The 'unbranched land plants with a single spore sac' (possibly representing the ancestral condition) may not (?) be a lineage, but those representing the change to branched plants with multiple spore sacs represents the possible lineage that ancestrially paved the way for new innovations in the major sublineages of vascular plants (those with well developed water and food conducting tissue, including lycophytes and euphyllophytes). In the past up to well into the 20th century, traditional botany (including taxonomic botany) dealt with additional life forms (e.g., algae, slime molds, fungi, lichens, and bacteria or certain other microscopic organisms) besides those with a land plant ancestry (= embryophytes) that are emphasized in this work. Although most of these additional organisms are now known to be distantly related to those most commonly referred to as "plants," their medicinal members will at times be included in this work to maintain the broad scope of traditional botany as once taught as a requirement for well trained apothecaries (early pharmacists) or physicians. Even medicinal organisms that are now known to be more closely related to animals (e.g., fungi) are sometimes included. There is even some mention of medicinal animals. Non-living, natural materials often considered minerals (such as medicinal lime or clay) are even occasionally listed in the main dictionary. Whenever known or felt appropriate, some chemistry of natural medicinal resources is featured in the paragraphs of the dictionary or linking pages. Although providing a traditional botany resource comparable to what was once available to well trained pharmacists or physicians, this work emphasizes a modern comparative method based on the genealogy (often supported by DNA) of living medicinal resources that does not completely overlook a possible correspondence of folk uses or medicinal properties with other characters or traits used in the classification and identification of these resources. Such an approach or perspective is discussed further below.

A medicinal genus is defined here as a group of one or more very closely related species that are found to be medicinal any where in the world. If a medicinal genus is found in New Mexico, this will be noted, along with some of its local species and (if also present) local subspecies or varieties; and this will be done even when the local plants are not recorded to be used medicinally in the state. The same applies to medicinal species. When such entries occur, the reader will usually be informed that the plants involved have likely medicinal properties, but no record of their use in New Mexico has yet been located. When two or more closely related species are found to be used for similar medicinal purposes in independent (widely separated) regions of the world or their uses correlate well with tested pharmacological activities of active chemicals (of at least one of the species), these uses (depending on how closely related the species) are considered statistically significant, not likely to occur by chance. The genus (or lower level), if it represents a well defined lineage, should be considered the most important category in taxonomy for the comparative study of statistically significant medicinal uses of closely related plants found anywhere in the world. Therefore, if a species of any of these genera (or lower levels) with statistically significant uses is known to be present in New Mexico, it will be listed in this dictionary, even though it is not known to be used medicinally in the state. Such statistically significant uses, especially those that pertain to plants at the level of the genus or below, can provide leads for the discovery (or re-discovery) of new (or forgotten) medicinal properties and also help to confirm the validity of known uses in New Mexico or elsewhere. See convergent uses.

Sometimes a "genus" or other formally named group can be poorly defined to include a polyphyletic combination of unrelated, superfically similar species. Such a traditionally named "genus" can include a certain proportion of species that are more closely related to other species in one or more other genera. This is one of the major reasons why certain (traditionally defined) scientific names often eventually get changed. In this work, an attempt is made to provide notes on important medicinal genera that still have such issues. Many "genera" of well-known, medicinal plants as traditionally defined still remain polyphyletic or paraphyletic. Name changes involving such artificially defined "genera", such as polyphyletic "Coreopsis" and "Ligusticum", will (sooner or later) have to be made. The accepted scientific names for tinctorial coreopsis (now Coreopsis tinctoria) and osha (now Ligusticum porteri) may not be the same in the near future. However, sometimes certain subgroups are segregrated from even a genus that represents a monophyletic group and these subgroups (segregrates) are given different genus names, thereby changing some species names of the previously defined genus. Such a proposal (annoying even to certain botanists) has recently been made (since 2017) for the medicinal genus Berberis. Of course, higher level group names can be charged in similar ways or sister groups that are given different names but that are similar enough in key characters for identification can sometimes be merged under a single name.

Contrary to what is often taught (as an ideal), there is not always just one preferred scientific name for the same species and their can be several alternative scientific names called synonyms that were often at one time or another considered preferred scientific names but have been rejected by a particular author or authors. The preferred name according to certain authors should also be distinguished from the correct name according to the ICBN Code. Sometimes the preferred name by most authors can be an incorrect name (a synonym) according to the ICBN. See example of this for the name Cardueae Cassini (= Thistle tribe) of the family Asteraceae. Recent DNA studies have lead to improvements in classifications that have resulted in multiple changes in names. Although often frustrating for people that do not want to have to keep up with the multitude of resulting new names, these improvements should not be considered a serious problem for those interested in names for real lineages (monophyletic groups) as apposed to artificial groups. However, when most revisions of the taxonomy have been regional rather than global, this can contribute to the confusion that has ensured the even more frustrating use of multiple taxonomic (scientific) names for the same species. See more on this problem and its attempted solution below.

According to Judd, et al. (2007), a synonym is "one of two or more names applied to the same taxon." However, according to ICBN a synonym is a rejected name by a particular author or authors either because the name is illegitimate (violates one or more ICBN rules) or because of poor taxonomic judgement, representing a poorly circumscribed (artificial) group (Simpson, 2006). This is because according to ICBN, each taxon (with a relatively few allowed exceptions) can have only one correct name. Therefore, a synonym is officially considered an example of a rejected name rather than just an alternative name. Furthermore, it is a rejected name according to a particular author or authors. Which name is correct or which name is considered a synonym may depend on which authors of which references are consulted. It should also be pointed out to the reader that each taxon can bear only one correct name, except for certain cases specified through special actions of botanical congresses. Certain widely used names that are not actually the earliest published according to ICBN rules can be allowed through these special actions to be considered correct names in order to avoid unnecessary name changes. The eight families with the oldest names [Compositae (= Asteraceae), Cruciferae (= Brassicaceae), Gramineae (= Poaceae), Guttiferae (= Clusiaceae), Labiatae (= Lamiaceae), Leguminosae (Fabaceae s.l.), Palmae (= Arecaceae), and Umbelliferae (= Apiaceae)] and one subfamily [Papilionoideae (= Faboideae)] are allowed by ICBN to have two correct names.

A correct name must (according to ICBN) be based on a type specimen, a pressed and dried plant mounted on a sheet of cardboard called a herbarium sheet deposited for reference in a herbarium (building where such specimens are kept safe and organized according to a classification system); or it can be an illustration of the plant. A type can, therefore, be an herbarium specimen or sometimes even an illustration chosen by taxonomists as being close or identical to that chosen by the original author as a designated representative of a plant name. The type for a particular genus name can be represented by the type specimen of a particular species name. For example, the type for the genus name Poa L. is represented by the type specimen of the species named Poa pratensis L. In other words, the genus name Poa L. can be said to be based on the species named Poa pratensis. The family name Poaceae or the order name Poales can be said to be based on the genus name Poa L. Therefore, it can be said that the type for the family name Poaceae or the order name Poales is the genus name Poa that can be represented by a type specimen for the species name Poa pratensis (= the type of the genus Poa). All this goes back to the most important contributions of Linnaeus to botany, which were the establishment of a binomial system of naming, an herbarium to authenticate the system of naming, and the arrangment of the herbarium sheets (pressed, dried plant specimens usually glued to a white, light weight cardboard backing placed in an enclosing folder made from lighter weight paper) according to a hierarchical system of classification. Actually prior to Linnaeus, the origin of the what is today called the 'herbarium' (referred to by various other names before Tournefort) has been attributed to the great Italian botany teacher Luca Ghina; and probably first established (as a larger scale effort) by Ghina's student Cesalpino. Nevertheless, the influential Linnaeus stressed its importance in botany and the naming and classification of plants. The preservation of pressed and dried plant samples (specimens) indexed by some kind of system of names for future reference has become almost necessary for the preservation of traditional medicinal knowledge. The archiving (the filing away for future reference) of permanent plant collections as herbarium specimens kept protected and organized by a system of classification within an herbarium to back up the plant names changed botanical taxonomy from an inexact art to a more exact science, making possible for the first time worldwide standardization of only one name for each species represented by one or more plant specimens. Synonyms can be based on the same or different type specimens; and they may be based on the same or different type specimens than the correct names.

The reasons that an accurate correspondence of names with preserved plant samples is an important step in the preservation of traditional medicinal knowledge can never be stressed enough in any written work dealing with plant names. Even much of the unrecorded, sacred medicinal knowledge of Native Americans not meant to be shared with outsiders can and should be preserved for future generations within these tribes by learning some lessions from the European history of botany. For example, before the herbarium (prior to the contributions of Ghina, Cesalpino, and Tournefort, re-inforced by the great influence of Linnaeus) or the preservation of pressed and dried plant samples (specimens) indexed by some kind of system of names for future reference, confusions in plant identification and even the retention of traditional medicinal knowledge became a serious problem in Europe. This became even more serious as the number of known plants began to rapidly increase by near the end of 15th and beginning of the 16th century with the European 'discovery' of the New World. Although a list of plant names without some kind of link to proper identification is next to useless, preserved plant samples accurately labeled by names can help provide such a link, which can also at least provide [by acting as vouchers (plant frames of reference)] an almost necessary means of entry for the preservation of traditional medicinal knowledge. For tribal peoples that are concerned about keeping their knowledge of the uses of medicinal plants from outsiders (or unauthorized/uninitiated tribal members) but that are losing many of their traditions, the preservation of pressed and dried medicinal plant specimens indexed by some kind of system of names (perhaps, only labeled with transcribed tribal plant names in addition to the more universal scientific names) for future reference would at least help solve many problems in proper plant identification, which usually become more severe as this knowledge begins to become less common. These plant samples could be used solely by authorized tribal members for reference in passing the private, unrecorded oral traditions about medicinal uses to future generations of their healers. This is why a work like this can provide important insights on preservation of traditional medicinal knowledge for people other than the outsiders without directly exposing that which is private to them.

In this work, the preferred or correct formal name is often immediately followed by a synonym in parentheses or brackets and the synonym is often preceded by an equal sign. Whenever a formal name is followed by a synonym in parentheses or brackets, there is also an attempt to clarify that the first name listed is the currently most accepted name. However, not all authors will always agree. In this work, sometimes a correct formal name is followed by a common name in parentheses or brackets and preceded by an equal sign or the order may be reversed. Two or more alternative common names are sometimes treated in a similar manner. If a genus name is the same as the common name, the genus name is often followed in parentheses by s.n. preceded by an equal sign. It is conventional for the synonym to be listed first followed by the correct formal name preceded by an equal sign. This convention is followed here only when the parentheses or brackets are not employed. In this case, a whole series of synonyms may be listed, each one separated by an equal sign; and the last name preceded by an equal sign is considered the correct name. In cases where a synonym is more commonly used than the correct name, the synonym is sometimes included first in the dictionary followed on the next line by the correct name preceded by an equal sign. This practice is applied to some recently changed names (e.g., the recent change of Acacia angustissima to Acaciella angustissima or Acacia greggii to Senegalia greggii).

When a list of updated genera names for a particular region (such as Mexico) is provided, sometimes a few common names of some of the species of the genera often separated by commas are listed in parentheses after a genus name and the list of common names is preceded by e.g. followed by a comma. The abbreviation e.g. is short for the Latin phrase exempli gratia, which means 'for example'. See such a listing of medicinal genera of Mexico in the plant family Asteraceae. This can be contrasted with the abbreviation i.e., which is short for the Latin id est, meaning in 'other words' or 'that is'.

It is important to emphasize that an up-to-date, authoritative, synonymized check-list for a geographical region under consideration is a basic necessity for collating common names with scientific names of plants reported to be used medicinally from diverse and sometimes fragmented sources that are available from the literature. This is especially true if older literature sources are accessed. As a starting point for this dictionary, synonyms (alternative scientific names other than the correct names) are usually only included for plants found in New Mexico, according to the check-list Flora Neomexicana I by Kelly W. Allred (cited as NM). This is an annotated checklist for the names of vascular plants in the State, with synonyms and bibliography. When available for a region, such synonymized check-lists often provide a listing of the most important scientific name synonyms for each up-to-date preferred scientific name for species, subspecies, and varieties. Each preferred scientific name or synonym is often listed under the family name. In an attempt to ensure the most up-to-date preferred or correct names, other resources on the web have also been consulted, such as relatively recent sections of Flora of North America (cited as FNA), Biota of North America Program (cited as BONAP), and Families and Genera of Vascular Plants (cited as KEW).

There is an effort by scientists to single out only one most up-to-date preferred or correct name for each species. However, when most revisions of the taxonomy of a genus, for example, have been regional rather than global, this can contribute to the confusion that has sometimes ensured the use of multiple taxonomic (scientific) names for the same species. Therefore, the need for a check-list of global scope has been stressed by the Global Strategy for Plant Conservation (UNEP). The Plant List (http://www.theplantlist.org/) is a attemped step toward an online flora of all known plants at the species level in the form of a global synonymized check-list.

Convergence of medicine uses

As stressed throughout this work, closely related organisms have overall more similarities in their characters or traits than more distantly related ones. Closely related plants often contain chemically similar secondary metabolites with pharmacodynamically similar actions. Therefore, it is also a rule of thumb that closely related plants often have larger numbers of correlating medicinal properties than more distantly related ones. In other words, closely related plants are often used by people (even in different parts of the world) in similar ways. The statistical significance of this rule becomes even greater when correlations in use of closely related plants are likely independent (found in separate regions of the world). Here, statistical significance refers to the possibility that these correlations in use are not due to mere coincidence. This adds to these uses more credibility (confidence or trust). Correlations of this type (often called ethnobotanical convergences) are likely due to independent discovery or invention. Therefore, convergent (correlating but independent) uses of closely related plants have often become some of the best leads for the discovery (or re-discovery) of new (or forgotten) medicinal properties. The more closely related medicinal plants are to each other within a geographically widespread lineage, the higher the chance that a larger number of commonalities (or at least some commonalities) in use of these plants can be found among people in different parts of the world. These similarities often are much closer than could possibly be accounted for on the basis of random chance. An inescapable conclusion (a likely hypothesis) is that such similarities are due to the fact that the plants so used are related to each other, derived from a common ancestor. The potential preservation of shared knowledge from the remote past that could show up today as medicinal use commonalities among people once living in close contact but currently living in separate (more or less independent) geographical regions cannot usually be distinguished from convergence. Therefore, such potential preservation is generally considered at least as statistically significant as convergence (see below for further comments). It is only the unique use commonalities of closely related plants among peoples in cultural contact in the more recent past that are expected to have a lower statistical significance. The common vagueness of folk use for various reasons can often be overcome by genealogical focusing on the more statistically significant convergent uses.

Of course, people of different cultures that are living in closer association with each other are, through the exchange of ideas between them, likely to have similar uses of the same plants, although there are sometimes exceptions to this for people living in close proximity but in very different environments. However, sometimes a branch of people will move away from their close relatives to a region surrounded by more distant relatives. In migration, human populations in new and unfamiliar territories may often select plants for use that are similar and often closely related to familiar resources of their prior homeland (another likely hypothesis). If this happens, some local plants may be used in some uniquely different ways by these migrated people, when compared to the uses of the same plants by their new and unrelated neighbors. Although borrowing between unrelated people living in close association is always likely to occur, the uses of some of the plants by migrated people may remain very different from their unrelated neighbors and more like their closer relatives further away. This represents statistically significant knowledge, because it likely has been retained for a considerable period of time. Although the possibility of cultural independence is higher among peoples that are geographically widely separated, this does not necessarily hold for widely separated peoples that were in cultural contact in the remote past. If there is evidence that widely separated peoples with a large number of current use commonalities were actually in contact in the remote past, it is always possible that they could have at the time shared knowledge with each other. The preservation of shared knowledge from the past that could show up today as medicinal use commonalities among people once living in close contact but currently living in separate (more or less independent) geographical regions should probably depending on how long they have been separated, be ranked higher in terms of statistical significance than independent discovery (convergence) of similar medicinal properties in closely related plants. However, even though some of these commonalities may indeed represent scattered remains of shared knowledge that has been preserved to this day, it is usually impossible to distinguish convergence from the potential of such a preservation, especially if its origins could conceivably be traced to the remote past. It is also possible that these widely separated peoples once in contact could have independently gained, lost, and regained over a long period of time many of their historically recorded use commonalities. The possibility of preservation of shared prehistoric medicinal knowledge among currently widely separated peoples is not denied. A section on the medicinal plant genus Artemisia is included only to suggest the means by which shared knowledge from the remote past among widely separated peoples once in contact could have been preserved. Although the use of Artemisia in the sweat lodge could be speculated to have originated in Eurasia from late Upper Paleolithic 'birth huts' used to facilitate labor and provide thermal regulation and protection for the women and baby, this narrative is in no way an attempt to demonstrate that scattered remains of a potentially 40,000 year old tradition shared by the Central Asian ancestors of both Europeans and Native Americans can still be found among the current uses of Artemisia by these (at least before 1492) widely separated descendants. Therefore, no attempt is generally made on this web site to try to distinguish such a potential preservation of shared knowledge from convergence. If the reader is interested, some other (mostly European) authors have written extensively on the potential preservation of shared medicinal plant knowledge from the remote past between the ancestors of Native Americans and Europeans. A recent book written in English, entitled 'The Untold History of Healing: Plant Lore and Medicinal Magic from the Stone Age to Present' by Wolf D. Storl (2017), provides additional input on this controversial but interesting topic. According to Dr. Bruno Wolters (2000a; 2000b), comparative studies indicate that today's (50-65%) commonality in use of closely related plants in Native American and Central European folk medicine is a relict from the Palaeolithic period; and he considered some of the medicinal plants common in the Northern Hemisphere circumpolar area to be the Pleistocene core of North American Indian medicine.

Genealogical focusing

A common way of attempting to measure the cluster density of folk uses within well defined lineages is to determine the percentage of the total number of recorded uses that are found in each of these lineages. The scope of this measurement can even be restricted to a well defined group, such as a genus. For example, 70% of the total number of recorded medicinal uses by Lukhoba, et al. (2006) mapped on a well-supported (DNA sequence based) genealogical tree for the genus Plectranthus [of Lamiaceae (mint family); subfamily Nepetoideae; tribe Ocimeae; subtribe Plectranthinae] are found in the subgroup of the genus represented by the well defined Coleus lineage (including species of the once separated genus Coleus, such as geographically widespread species Plectranthus barbatus, Plectranthus amboinicus, and Plectranthus mollis).

The quantitively determined phylogenetic patterns in traditional medicinal plant use (involving the mapping of similar folk medicinal uses for related health problems on DNA sequence based genealogical trees) in three independent regions has already made science news (Saslis-Lagoudakis, et al., 2012), rendering it less likely that folk knowledge about medicinal plants (sometimes construed as 'old wives tales') is based solely on magic, superstition, or some other factors besides bioactive chemical properties.

In this dictionary, even though focusing on specific regions (New Mexico and Morelos), an attempt is made to maintain a global perspective. Often plants are listed in this dictionary that grow wild in New Mexico that are considered important medicinal resources elsewhere in the world but little or no known reports may exist that indicate medicinal use of these resources in the state. For example, this appears to be the case in New Mexico for the genera Anaphalis, Gnaphalium, and Pseudognaphalium. Unfortunately, no information can yet be found that any of the species now assigned to Pseudognaphalium were ever actually used as medicinals by the Spanish New Mexicans. No reports could be found that Spanish New Mexicans ever used any of the species of the above genera; and only two reports (Moerman from http://herb.umd.umich.edu/) could be found that Native Americans in New Mexico have traditionally used certain species of Pseudognaphalium (i.e., P. canescens and P. stramineum) for some medicinal purpose. Nevertheless, if there is a high degree of consistency in the reports on use of closely related medicinal resources over a wide geographical area or especially in different (geogrphically independent) regions of the world, these are the reports on use emphasized and discussed in more detail in this work for plants growing wild in New Mexico, even when there are few or no reports for use of these plants in the state. It is emphasized in this work that closely related plants, even when present in different, sometimes geographically independent regions of the world, are often used for similar medicinal purposes; and these uses can sometimes even 'reflect' (or correlate with) the genealogical relationships between the plants. In various regions occupied by people of a similar culture and the same language (e.g., Spanish), similar names are often given to closely related or sometimes more distantly related plants that can be used for similar medicinal purposes. See also some notes on plants commonly referred to as Gordolobo in Spanish.

In this dictionary, there is an attempt to update the listing of family names for flowering plants on the basis of APG II, III, and IV (Angiosperm Phylogeny Group, 2003, 2009, and 2016). This is based on the main principle of Backlund and Bremer (1998) that groups of organisms recognized by formal names should represent true (monophyletic) lineages. For each flowering plant family name, there is included, according to APG IV (2009), the name of the order in which the family is a member. See attempt to rank order the names of families of flowering plants (as defined by APG III & IV) in a way that broadly 'reflects' genealogy. Family names for vascular plants together with names of some of their broader lineages are also featured according to Cantino, et al. (2007) and (for ferns and their relatives) Smith, et al. (2006). Therefore, some preferred family names may not always be the same as those listed for the genera, species, subspecies, or varieties in some of the consulted check-lists. Preferred family names are listed like other entries in alphabetical order of the first word in the paragraphs. When the family name of a consulted check-list (e.g., NM) is different from the preferred name listed, this is often noted in the paragraph including the preferred name. Because most ranks above order are not emphasized in this work and classification is based (as much as possible) on genealogical relationships of lineages, each of the paragraphs in the dictionary with a family name as first word also provides a nested hierarchy of less inclusive to more inclusive names of lineages. These are the names of the more inclusive lineages that include the family and its order. Because these named lineages correspond to sections of the tree of life, the reader can eventually learn the named lineages as a means of locating a particular family on the tree of life. See also attempt to rank order all green plants (= viridophytes) elsewhere.

There have been published attempts to construct working, rank ordered classifications the reflect genealogy for viridophytes (Lewis & McCourt (2004)) and for embryophytes with an emphasis on flowering seed plants (Chase & Reveal (2009)).

The example below includes all entries (common and scientific names) found in the dictionary that apply to the genus Achillea L. (common name: yarrow) and its single New Mexican species. The dash symbol (-) acts as a delimiter used to place words or phrases in separate columns for a spread sheet. When importing the dictionary to a spread sheet or data base, use the dash symbol followed by the space bar to create the columns. Each entry is delimited by two end of line spaces and can be treated as a paragraph. Again (see above for more details), each entry (a scientific or common name, etc.) is in alphabetical order according to the first word in its paragraph. It should be noted that the L. following the genus name Achillea represents the abbreviation for the author of the genus name. This author happens to be Carl Linnaeus. Achillea millefolium L. is a common species in New Mexico. Several full scientific names called synonyms (including the authors of the names) are listed prior to some notes.
-------------------------------------------------------------------
Achillea
Achillea millefolium
Asteraceae
Abrofia
Achilea
Alcaina
Alcanfor
Alcanforero
Altarreina
Alterraina
Aquilea
Aquiléia
Artemisa bastarda
Bloodwort
Camomila de los montes
Carpenter's weed
Ciento en rama
Cientoenrama
Ciprés de invierno
Ciprés de Judea
Ciprés de perla
Colchón de pobre
Common yarrow
Erva carpinteira
Erva das cortadelas
Erva de São João
Erva do Bom Deus
Erva dos carpinteiros
Erva dos golpes
Erva dos militares
Erva dos soldados
Feiteirinha
Feteirinha
Flor de la pluma
Flor de pluma
Gordolobo
Herva do carpintero
Hierba carpintera
Hierba de Aquiles
Hierba de la cortadura
Hierba de la muela
Hierba de las cortaduras
Hierba del carpintero
Hierba del cortes
Milflor
Milfoil
Milfolhada
Milfolio
Milhojas
Millenrama
Nosebleed
Old man
Pluma de la tierra
Plumajillo
Plumajo
Prazer das damas
Real de oro
Salvaçao do mundo
Sereno de invierno
Sneezeweed
Staunchgrass
Thousand seal
Tlalquequesal
Tlaquequetzal
Viuda
Western yarrow
Yarrow
Yarrow (common)
---------------------------------------------------------------------------------

Acording to Encyclopedia of Life (http://eol.org/pages/467225/overview),
the several varieties and subspecies of Achillea millefolium (common yarrow) in the world include:

All the genera of vascular plants in New Mexico with known medicinal species will eventually be listed under the formal name of the family in which they belong. As an example for at least a partial list of genera in the family Asteraceae, a single asterisk is placed in front of the genus name, if one or more of its species are known (recorded) to be used medicinally anywhere in the world. A double asterisk indicates that one or more of the species of the genus are also considered medicinal in Morelos. This can be updated as additional information is found. It is hoped that eventually all the medicinal genera of the families of vascular plants will be provided with single or double asterisks. For each genera listed under a particular family, the common name of this genus given by BONAP or NM with a preceding equal sign is placed in parentheses following its formal name; and a common name that is the same as the formal one can be indicated by s.n. Another equal sign following the common name sometimes precedes a possible, alternative preferred name or synonym (according to some other modern authority, e.g., Mabberley, 1997). As the other names included in the dictionary, all family names are listed in alphabetical order. Those genera with one or two preceding asterisks (listed under the each family) are also placed in alphabetical order as separate entries in the dictionary. In other words, the formal names for each medicinal genus with a single or double asterisk listed under the family can also be looked up in alphabetical order in the dictionary. Under each of these entries for the genera can be found additional English, Spanish, Aztec or Mayan common names. All the species names in New Mexico are listed under the formal name for each medicinal genus. This listing of species names will eventually include single and double asterisks as in the listing of genera under the family. Each medicinal species can in turn be looked up under its formal name in alphabetical order to obtain additional English, Spanish, Aztec or Mayan common names. Under the formal name of each medicinal species is included (if present in New Mexico) formal subspecies or variety names. This is an attempt to maintain a systematic arrangement (a natural organization of scientific names as a nested hierarchy of lineages) and at the same time everything medicinal at the level of genus, species, variety, or subspecies (at least growing wild in New Mexico) can be conveniently looked up in alphabetical order. The order or higher level lineage name that each family belongs to can be found under the family name. Some of these higher level lineage names (including those applying to orders) have been published as formal names but others can pertain to informal names. Furthermore, some of the informal higher level lineage names listed under the formal family name in the dictionary may have been given published formal names. There is no attempt in the dictionary itself to list in alphabetical order any of these higher level lineage names above family. However, they can often be found listed at least for vascular plants in a systematic order or arrangement on a page dealing with higher level lineages to be eventually added. Some other published formal lineage names above or below the level of family can often be found elsewhere on some of the pages to be added. Eventually, the main dictionary will be linked to these additional pages. However, if all the possible names (formal or informal) for all the possible lineages and sublineages were actually listed in alphabetical order, the dictionary of names might become too voluminous for practical lookup of common and scientific names of medicinal organisms. Therefore, the dictionary itself lists in alphabetical order the formal names of medicinal organisms (at least those vascular plants known to grow wild in New Mexico) applying only to the levels of family, genus, species, and variety or subspecies. In turn, the common names are associated with the formal names applying to these levels. However, there is even an open question as to whether the listing of every possible Spanish or English common name for every medicinal in every local region of North America would prove practical, because a hard copy of such a dictionary might become too bulky for easy manual lookup. Where to draw the lines of limitations on all this is still open to several future considerations. Therefore, this dictionary is initially being constructed by focusing on only two states, New Mexico and Morelos. With the added pages, this work is likely to eventually at least serve as a comprehensive medicinal flora of New Mexico with information added especially for Morelos and sometimes for other regions in North America, especially the Southwest USA and adjacent Northern Mexico.

The name of the family in which the genus Achillea is a member is included here (as an example) with (at least) the following information included:

Asteraceae - Martynov - (APG III) Family Name
(= Compositae Giseke)
Asterales - Lindl. - (APG III) Order Name
Higher level lineages:
Angiospermae; Mesangiospermae;
Eudicotyledoneae (= eudicots);
Gunneridae (= core eudicots);
Pentapetalae; Asteridae (= asterids);
Gentianidae (= euasterids or core asterids);
Campanulidae; Apiidae (= euasterid II = asterid II).
Some of the highest level lineages:
Embryophyta (Land Plant); Polysporangiophytes; Tracheophyta
(eutracheophytes); Euphyllophyta; Spermatophyta (seed plants)
In Morelos, a listing of 32 medicinal genera includes: - - (Atlas-Mexico)
**Achillea L., Alomia Kunth, **Artemisia L., **Baccharis L.,
Barkleyanthus H.Rob. & Brettell, **Bidens L., **Brickellia Elliott,
Calea L., Calendula L., **Cirsium Mill., **Cosmos Cav.,
**Dyssodia Cav., **Erigeron L., **Eupatorium L., **Gnaphalium L.,
**Heterotheca Cass., Iostephane Benth., **Matricaria L.,
Mikania Willd., Montanoa Cerv., **Pinaropappus Less.,
Piqueria Cav., **Pluchea Cass., **Porophyllum Adans.,
**Sanvitalia Lam., **Schkuhria Roth, Sclerocarpus Jacq., **Sonchus L.,
**Tagetes L., **Tanacetum L., Tridax L., and **Verbesina L.
**Genus found in New Mexico with one or more species reported
to be considered medicinal in Morelos.
In New Mexico, the Asteraceae is a well represented family - - (BONAP, NM)
with the following 167 genera:
**Achillea L. (= Yarrow), *Acourtia D. Don (= Desertpeony),
Acroptilon Cass. (= s.n.), Adenophyllum Pers. (= Dogweed),
*Ageratina Spach (= Snakeroot), *Ageratum L. (= s.n.),
*Agoseris Raf. (= s.n.), Almutaster A.& D. Love (= ?) = Aster,
*Ambrosia L. (= Ragweed), Amphiachyris (A. DC.) Nutt. (= s.n.),
*Anaphalis DC. (= Pearlyeverlasting), *Antennaria Gaertn. (= Pussytoes),
*Anthemis L. (= Chamomile),
Antheropeas Rydb. (= Easterbonnets) = Eriophyllum Lagasca.,
Aphanostephus DC. (= Dozedaisy), *Arctium L. (= Burrdock),
*Arnica L. (= s.n.), **Artemisia L. (= Sagebrush),
*Aster L. (= s.n.), **Baccharis L. (= s.n.),
*Bahia Lag. (= s.n.), Baileya Harvey & Gray ex Gray (= s.n.),
Bartlettia Gray (= s.n.), Bebbia Greene (= s.n.),
*Berlandiera DC. (= s.n.), **Bidens L. (= Beggartick),
Brachyactis Ledeb. (= Rayless aster), **Brickellia Ell. (= s.n.),
Calycoseris Gray (= Tackstem), Calyptocarpus Less. (= s.n.),
Carduus L. (= Plumeless thistle), Carminatia Moc. ex DC. (= s.n.),
Carphochaete Gray (= Bristlehead), *Carthamus L. (= Distaff thistle),
*Centaurea L. (= Star thistle), Chaenactis DC. (= s.n.),
*Chaetopappa DC. (= Leastdaisy), Chamaechaenactis Rydb. (= s.n.),
*Chaptalia Vent. (= Sunbonnetts), *Chloracantha Nesom (= s.n.),
*Chrysactinia Gray (= s.n.), *Chrysothamnus Nutt. (= Rabbitbrush),
*Cichorium L. (= Chicory), **Cirsium P. Mill. (= Thistle),
*Conyza Less. (= Horseweed), *Coreopsis L. (= Tickseed),
**Cosmos Cav. (= s.n.), *Crepis L. (= Hawksbeard),
Dicoria Torr. ex Gray (= s.n.), Dicranocarpus Gray (= s.n.),
Dracopis Cass. (= Coneflower), **Dyssodia Cav. (= s.n.),
*Echinacea Moench (= Purple coneflower), *Eclipta L. (= s.n.),
*Encelia Adans. (= Brittlebush), Engelmannia Gray ex Nutt. (= s.n.),
*Ericameria Nutt. (= Heathgoldenrod), **Erigeron L. (= Fleabane),
*Eupatorium L. (= Thoroughwort), Euthamia Nutt. ex Cass. (= Goldentop),
Evax Gaertn. (= Pygmy cudweed) = Filago, Filago L. (= Cottonrose),
Flaveria Juss. (Yellowtops), Flourensia DC. (Tarwort),
*Gaillardia Foug. (= s.n.), Galinsoga Ruiz & Pavon (= s.n.),
**Gnaphalium L. (= Cudweed), *Grindelia Willd. (= Gumweed),
*Gutierrezia Lag. (= Snakeweed), Gymnosperma Less. (= s.n.),
Haploesthes Gray (Falsebroomweed), *Helenium L. (= Sneezeweed),
Helianthella Torr. & Gray (= s.n.), *Helianthus L. (= Sunflower),
Heliopsis Pers. (= s.n.), Heliomeris Nutt. (= s.n.),
Herrickia Woot. & Standl. (= s.n.) = Aster, Heterosperma Cav. (= s.n.),
**Heterotheca Cass. (= Telegraphplant), *Hieracium L. (= Hawkweed),
*Hymenoclea Torr. & Gray ex Gray (= Burrobush),
*Hymenopappus L'Her. (= s.n.), Hymenothrix Gray (= s.n.),
*Hymenoxys Cass. (= s.n.), *Hypochaeris L. (= Catsear),
Ionactis Greene (= s.n.), *Isocoma Nutt. (= s.n.), *Iva L. (= s.n.),
Jefea Stother (= s.n.), Krigia Schreb. (= s.n.),
*Lactuca L. (= Lettuce), Laennecia Cass. (= s.n.),
Lasianthaea DC. (= s.n.), Lasthenia Cass. (= s.n.),
Layia Hook. & Arn. ex DC. (= Tidytips), Leibnitzia Cass. (= s.n.),
Lepidospartum (Gray) Gray (= Broomsage),
*Leucanthemum P. Mill. (= s.n.),
*Liatris Gaertn. ex Schreb. (= Gayfeather),
*Lygodesmia D. Don (= Skeletonplant),
*Machaeranthera Nees (= s.n.), *Madia Molina (= Tarweed),
*Malacothrix DC. (= s.n.), **Matricaria L. (= Mayweed),
Melampodium L. (= s.n.), Nicolletia Gray (= s.n.),
Nothocalais (Gray) Greene (= s.n.), Oligoneuron Small (= ?),
*Onopordum L. (= Cottonthistle), Palafoxia Lag. (= s.n.),
Parthenice Gray (= s.n.), *Parthenium L. (= Feverfew),
*Pectis L. (= Fetid marigold), *Pentzia Thunb. (= s.n.),
*Pericome Gray (= s.n.), Perityle Benth. (= Rockdaisy),
*Petradoria Greene (= Rockgoldenrod),
*Picradeniopsis Rydb. ex Britt. (= Bahia) = Bahia,
**Pinaropappus Less. (= Rocklettuce), Platyschkuhria Rydb. (= s.n.),
**Pluchea Cass. (= s.n.), **Porophyllum Adans. (= s.n.),
Prenanthella Rydb. (= s.n.), *Psacalium Cass (= s.n.),
*Psathyrotes Gray (= s.n.), Pseudoclappia Rydb. (= s.n.),
*Pseudognaphalium Kirp. (= ?), Psilactis Gray (= ?),
*Psilostrophe DC. (= Paperflower), *Pyrrhopappus DC. (= Desertchicory),
Pyrrocoma Hook. (= s.n.), Rafinesquia Nutt. (= California chicory),
*Ratibida Raf. (= Prairie coneflower), *Rudbeckia L. (= Coneflower),
**Sanvitalia Lam. (= s.n.), Sartwellia Gray (= s.n.),
**Schkuhria Roth (= False threadleaf), Scorzonera L. (= s.n.),
*Senecio L. (= Groundsel), *Silphium L. (= Rosinweed),
*Silybum Adans. (= Milkthistle), Simsia Pers. (= Bushsunflower),
*Solidago L. (= Goldenrod), **Sonchus L. (= Sowthistle),
*Stenotus Nutt. (= s.n.), *Stephanomeria Nutt. (= Wirelettuce),
*Stevia Cav. (= Candyleaf), Stylocline Nutt. (= s.n.),
**Tagetes L. (= Marigold), **Tanacetum L. (= Tansy),
*Taraxacum G.H. Weber ex Wiggers (= Dandelion),
*Tetraneuris Greene (= Hymenoxys), *Tetradymia DC. (= Horsebrush),
*Thelesperma Less. (= Greenthread), *Thymophylla Lag. (= s.n.),
Tonestus A. Nels. (= s.n.), *Townsendia Hook. (= s.n.),
*Tragopogon L. (= Goatsbeard), *Trixis P. Br. (= s.n.),
Uropappus Nutt. (= ?), **Verbesina L. (= Crownbeard),
*Vernonia Schreb. (= Ironweed), Viguiera Kunth (= Goldeneye),
*Wyethia Nutt. (= s.n.), *Xanthisma DC. (= Xanthium),
*Xanthium L. (= Cocklebur), and *Zinnia L. (= s.n.).
*Genus found in New Mexico with one or more species reported
to be used medicinally somewhere in the world.
**Genus found in New Mexico with one or more species reported
to be considered medicinal in Morelos.
See notes.

The main Spanish/English/scientific names dictionary will eventually be supported by links to other pages. These include pages on botany, medicinal properties, and even plant fossils that are not organized by the alphabetical order of any system of names, but (as much as possible) according to the order of branching of lineages. However, there are two glossaries, including subject names and botanical terms useful in identification that are placed in alphabetical order. The information on fossils is provided to help support lineages, genealogical relationships (branching pattern of ancestor-descendant relationships due to evolution), or even locate uncertain evolutionary relationships on the tree of life. An attempt is made to extensively interlink all pages with each other. The pages organized on the basis of genealogical relationships aid the reader in developing a better understanding of the distribution of medicinal properties in various lineages. An attempt is made here to address all the issues involved in the study of living medicinal remedies by integrating as much as possible the classification and identification (involving what is called systematic biology or botany) with the properties and uses of these natural resources.

The organization of nature does not center around human beings and their needs. Our uses of living medicinal resources depend on our ability to find an application for properties provided within the framework of the natural order. In this way our uses of living medicinal resources depend and often can even reflect the natural order referred to here as genealogical relationships, which influence and are influenced by ecological relationships between living organisms and the environment. Once it can be recognized that medicinal properties of plants or other organisms tend to be organized in nature according to genealogical relationships of these resources, the more natural genealogical perspective can be used as a complementary but alternative approach to lists of remedies artificially organized in alphabetical order or on the basis of how they can be employed to treat health conditions pertaining to the systems of the human body. This genealogical approach is necessary in developing a general "birds-eye view" of the medicinal resource potential of larger and larger numbers of living resources used by people throughout the world. This systematic arrangement allows for the possibility of showing that a significant percentage of medicinal information can fall together on the basis of major lineages and sublineages of the living resources, which can enable more efficient storage and retrieval of specific information at the same time as providing a broader perspective that can often help the reader remember or keep track of the major properties of a wider diversity of living medicinal resources. On the other hand, this broad perspective can be employed to help the reader narrow down and understand the properties of specific medicinal resources in the regions of interest, namely the Southwest USA, focusing on New Mexico, and the often much more diverse regions of Mexico, focusing on Morelos. The genealogical perspective offered here can even aid the herbalist that wants to adopt only a small collection of highly effective medicinal resources, because such a reader can be selective in excessing the links of these pages that address information on his or her choice medicinal plants to learn how to identify these remedies and distinguish them from others in the same or different lineages. When searching for alternative remedies with similar medicinal properties, such remedies are often concentrated in specific (relatively narrow) lineages; however, due to independent development of similar properties, alternatives can also be found in different lineages. The search for an alternative remedy to one that may not grow in the region of the herbalist can be greatly aided by this genealogical perspective. If a species of interest does not grow in a particular region but other members of the specific lineage of this species can be found, the herbalist can make an attempt to selectively uncover traditional use information for these alternative species. Potential alternative species that grow wild in New Mexico for genera will often be listed in the main Spanish/English/scientific names dictionary. Uncovered traditional use information for any of these species can often aid (as statistical confirmation) in selecting the ones most likely valuable as alternatives. If no members of a specific lineage can be found growing wild in the region, the quest for a local alternative becomes more difficult, but more inclusive lineages or different lineages can be searched for one or more species with the sought-after properties or traditional use patterns. The genealogical perspective can often provide a well-defined frame of reference for such a search. The genealogical perspective also provide the most efficient means for organizing information that can aid in the classification and identification of organisms of medicinal interest. Without this perspective the learning process often becomes the memorization of artificially organized information that is not always easily assimilated. Without any understanding of how to recognize the diagnostic characters that aid in the identification of medicinal resources and how major medicinal properties often can be associated with specific lineages, the reader is left with lists of medicinal resources that he or she cannot easily identify in the wild. Many species in these lists may not even grow wild in the region where the reader resides.

Also, knowledge presented in this work for similar medicinal properties and uses of closely related plants by the "five figures" humans (here and there) all over the world (even in relatively independent geographical regions) should not be considered a threat to the privacy of more local tribal medicinal knowledge, but it should rather be considered re-inforcement to help preserve this more local knowledge. Even those medicinal plants found only in one restricted area may sometimes have fairly close relatives with similar properties and uses known elsewhere in the world.

The student of herbs should also be at least aware of other related fields, such as biochemistry, biology and botany, chemical ecology, comparative biology, comparative phytochemistry, ecology, ethnobotany and ethnobiology, ethnopharmacology, genetics, paleobotany, pharmacognosy, pharmacology, pharmacophylogeny, phylogenetic systematics, systematics and taxonomy, and zoopharmacognosy.

Basic to description, identification, nomenclature (naming), and classification (= systematic arrangement) of medicinal plants is an understanding of plant characters or traits. See plant characters, heritable polymorphic traits, evolution of genuine characters, genuine characters and their states, nonheritable traits, molecular characters, morphological characters from fossils, bioactive chemical characters and plant genealogy, difficult character definition, cryptic characters (example), reversals, parallelisms and convergences, and shared divergent characters.

Table 1. A listing of important family names (in alphabetical order) are as follows:
Acanthaceae, Acoraceae, Adoxaceae, Agavaceae, Alliaceae, Altingiaceae, Amaranthaceae, Anacardiaceae, Annonaceae, Apiaceae, Apocynaceae, Araceae, Arecaceae, Aristolochiaceae, Asphodelaceae, Asteraceae, Begoniaceae, Betulaceae, Bignoniaceae, Boraginaceae, Brassicaceae, Burseraceae, Cactaceae, Cannabaceae, Caprifoliaceae, Caricaceae, Cistaceae, Commelinaceae, Convolvulaceae, Crassulaceae, Cucurbitaceae, Cupressaceae, Dennstaedtiaceae, Dryopteridaceae, Ebenaceae, Equisetaceae, Ericaceae, Euphorbiaceae, Fabaceae, Fagaceae, Gentianaceae, Geraniaceae, Krameriaceae, Lamiaceae, Lauraceae, Loranthaceae, Lythraceae, Malpighiaceae, Malvaceae, Meliaceae, Moraceae, Myrtaceae, Nyctaginaceae, Oleaceae, Onagraceae, Orobanchaceae, Papaveraceae, Phytolaccaceae, Pinaceae, Piperaceae, Plantaginaceae, Plumbaginaceae, Poaceae, Polygalaceae, Polygonaceae, Polypodiaceae, Portulacaceae, Primulaceae, Pteridaceae, Ranunculaceae, Rosaceae, Rubiaceae, Rutaceae, Santalaceae, Sapindaceae, Sapotaceae, Schisandraceae, Scrophulariaceae, Selaginellaceae, Simaroubaceae, Smilacaceae, Solanaceae, Theaceae, Tropaeolaceae, Turneraceae, Urticaceae, Valerianaceae, Verbenaceae, Violaceae, Vitaceae, and Zygophyllaceae.
These family names are also included in the main list--with author(s) and classification system based on DNA, including orders and higher level lineages.
The families can be grouped into orders. The order name is a single word ending in the suffix -ales. Finally, the orders can be grouped into a series of lineages with the more inclusive lineages listed before the less inclusive ones. The genera and species composition of the families, orders, and other lineages listed in this dictionary have been largely supported by DNA evidence.

Table 2. Key Medicinal Genera of Morelos, Mexico* [numbered in alphabetical order (with family in brackets)]:
Do search on medicinal plants of Mexico; medicinal plants of Morelos.
1. Acacia - P. Mill. - [Fabaceae],
2. Acalypha - L. - [Euphorbiaceae],
3. Achillea - L. - [Asteraceae],
4. Agastache - Gronov. - [Lamiaceae],
5. Agave - L. - [Agavaceae],
6. Alchemilla - L. - [Rosaceae],
7. Allium - L. - [Alliaceae],
8. Aloe - L. - [Aloaceae (= Asphodelaceae)],
9. Alomia - Kunth - [Asteraceae],
10. Aloysia - Juss. - [Verbenaceae],
11. Ampelopsis - Michx. - [Vitaceae (= Vitidaceae)],
12. Amphipterygium - Schiede ex Standl.
= Juliania - Schltdl.(SUH) - [Anacardiaceae (Julianaceae)],
13. Anagallis - L. - [Primulaceae],
14. Annona - L. - [Annonaceae],
15. Anoda - Cav. - [Malvaceae],
16. Apium - L. - [Apiaceae],
17. Arachis - L. - [Fabaceae],
18. Arctostaphylos - Adans. - [Ericaceae],
19. Argemone - L. - [Papaveraceae],
20. Aristolochia - L. - [Aristolochiaceae],
21. Artemisia - L. - [Asteraceae],
22. Arundo - L. - [Poaceae],
23. Asclepias - L. - [Asclepiadaceae (now placed within Apocynaceae)],
24. Baccharis - L. - [Asteraceae],
25. Bacopa - Aubl. - [Scrophulariaceae (now placed in Plantaginaceae)],
26. Barkleyanthus - H.Rob. & Brettell - [Asteraceae],
27. Begonia - L. - [Begoniaceae],
28. Bidens - L. - [Asteraceae],
29. Bocconia - L. - [Papaveraceae],
30. Boerhavia - L. - [Nyctaginaceae],
31. Borago - L. - [Boraginaceae],
32. Borreria - G.Mey. = Spermacoce - L. - [Rubiaceae],
33. Bougainvillea - Comm. ex Juss. - [Nyctaginaceae],
34. Bouvardia - Salisb. - [Rubiaceae],
35. Brassica - L. - [Brassicaceae],
36. Brickellia - Elliott - [Asteraceae],
37. Brugmansia - Pers. - [Solanaceae],
38. Buddleja - L. - [Buddlejaceae (now placed in Scrophulariaceae)],
39. Bunchosia - Rich. ex Kunth - [Malpighiaceae],
40. Bursera - Jacq. ex L. - [Burseraceae],
41. Byrsonima - Rich. ex Kunth - [Malpighiaceae],
42. Caesalpinia - L. - [Fabaceae],
43. Calea - L. - [Asteraceae],
44. Calendula - L. - [Asteraceae],
45. Calliandra - Benth. - [Fabaceae],
46. Cannabis - L. - [Cannabaceae (Cannabidaceae)],
47. Capsicum - L. - [Solanaceae],
48. Carica - L. - [Caricaceae],
49. Casimiroa - La Llave - [Rutaceae],
50. Cassia - L. - [Fabaceae],
51. Castilleja - Mutis ex L.f. - [Scrophulariaceae (now placed in Orobanchaceae)],
52. Cedrela - P.Browne - [Meliaceae],
53. Cestrum - L. - [Solanaceae],
54. Cinnamomum - Schaeff. - [Lauraceae],
55. Cirsium - Mill. - [Asteraceae],
56. Cissus - L. - [Vitaceae (= Vitidaceae)],
57. Citrus - L. - [Rutaceae],
58. Clematis - L. - [Ranunculaceae],
59. Cocos - L. - [Arecaceae],
60. Coffea - L. - [Rubiaceae],
61. Commelina - L. - [Commelinaceae],
62. Cordia - L. - [Boraginaceae (Ehretiaceae)],
63. Cosmos - Cav. - [Asteraceae],
64. Crataegus - L. - [Rosaceae],
65. Crescentia - L. - [Bignoniaceae],
66. Crotalaria - L. - [Fabaceae],
67. Croton - L. - [Euphorbiaceae],
68. Cucurbita - L. - [Cucurbitaceae],
69. Cunila - Royen ex L. - [Lamiaceae],
70. Cuphea - P.Browne - [Lythraceae],
71. Cupressus - L. - [Cupressaceae],
72. Cydonia - Mill. - [Rosaceae],
73. Cynodon - Rich. - [Poaceae],
74. Datura - L. - [Solanaceae],
75. Didymaea - Hook.f. - [Rubiaceae],
76. Diospyros - L. - [Ebenaceae],
77. Dodonaea - Mill. - [Sapindaceae],
78. Dorstenia - L. - [Moraceae],
79. Dryopteris - Adans. - [Dryopteridaceae],
80. Dyssodia - Cav. - [Asteraceae],
81. Equisetum - L. - [Equisetaceae],
82. Erigeron - L. - [Asteraceae],
83. Eriosema - (DC.) Rchb. - [Fabaceae],
84. Erythrina - L. - [Fabaceae],
85. Eucalyptus - L'Her. - [Myrtaceae],
86. Eugenia - L. - [Myrtaceae],
87. Eupatorium - L. - [Asteraceae],
88. Euphorbia - L. - [Euphorbiaceae],
89. Eysenhardtia - Kunth - [Fabaceae],
90. Ficus - L. - [Moraceae],
91. Foeniculum - Mill. - [Apiaceae],
92. Fraxinus - L. - [Oleaceae],
93. Galphimia - Cav. - [Malpighiaceae],
94. Gentiana - L. - [Gentianaceae],
95. Geranium - L. - [Geraniaceae],
96. Gliricidia - Kunth - [Fabaceae],
97. Gnaphalium - L. - [Asteraceae],
98. Guazuma - Mill. - [Sterculiaceae (now placed in Malvaceae)],
99. Haematoxylum - L. - [Fabaceae],
100. Hedeoma - Pers. - [Lamiaceae],
101. Heimia - Link - [Lythraceae],
102. Helianthemum - Mill. - [Cistaceae],
103. Heterotheca - Cass. - [Asteraceae],
104. Hura - L. - [Euphorbiaceae],
105. Hyptis - Jacq. - [Lamiaceae],
106. Illicium - L. - [Illiciaceae (now placed in Schisandraceae)],
107. Iostephane - Benth. - [Asteraceae],
108. Ipomoea - L. - [Convolvulaceae],
109. Iresine - P.Browne - [Amaranthaceae],
110. Jatropha - L. - [Euphorbiaceae],
111. Justicia - L. - [Acanthaceae],
112. Krameria - L. ex Loefl. - [Krameriaceae],
113. Lantana - L. - [Verbenaceae],
114. Larrea - Cav. - [Zygophyllaceae],
115. Leonotis - (Pers.) R.Br. - [Lamiaceae],
116. Lepechinia - Willd. - [Lamiaceae],
117. Lepidium - L. - [Brassicaceae],
118. Leucaena - Benth. - [Fabaceae],
119. Lippia - L. - [Verbenaceae],
120. Liquidambar - L. - [Hamamelidaceae (now placed in Altingiaceae)],
121. Litsea - Lam. - [Lauraceae],
122. Lopezia - Cav. - [Onagraceae],
123. Lysiloma - Benth. - [Fabaceae],
124. Malpighia - L. - [Malpighiaceae],
125. Malva - L. - [Malvaceae],
126. Malvaviscus - Fabr. - [Malvaceae],
127. Mangifera - L. - [Anacardiaceae],
128. Marrubium - L. - [Lamiaceae],
129. Matricaria - L. - [Asteraceae],
130. Medicago - L. - [Fabaceae],
131. Melia - L. - [Meliaceae],
132. Mentha - L. - [Lamiaceae],
133. Mikania - Willd. - [Asteraceae],
134. Mimosa - L. - [Fabaceae],
135. Mirabilis - L. - [Nyctaginaceae],
136. Montanoa - Cerv. - [Asteraceae],
137. Murraya - L. - [Rutaceae],
138. Nerium - L. - [Apocynaceae],
139. Nicotiana - L. - [Solanaceae],
140. Ocimum - L. - [Lamiaceae],
141. Oenothera - L. - [Onagraceae],
142. Origanum - L. - [Lamiaceae],
143. Oryza - L. - [Poaceae],
144. Pachyrhizus - Rich. ex DC. - [Fabaceae],
145. Parmentiera - DC. - [Bignoniaceae],
146. Pedilanthus - Neck. ex Poit. - [Euphorbiaceae],
147. Pelargonium - L'Her. ex Aiton - [Geraniaceae],
148. Penstemon - Schmidel - [Scrophulariaceae (now placed in Plantaginaceae)],
149. Peomus - ? - [?],
150. Persea - Mill. - [Lauraceae],
151. Petiveria - L. - [Petiveriaceae = Phytolaccoideae/Rivinoideae of Phytolaccaceae],
152. Petroselinum - Hill - [Apiaceae],
153. Phlebodium - (R.Br.) J.Sm. - [Polypodiaceae (Polypodioid)],
154. Phoenix - L. - [Arecaceae],
155. Phoradendron - Nutt. - [Santalaceae (Viscaceae)],
156. Physalis - L. - [Solanaceae],
157. Phytolacca - L. - [Phytolaccaceae],
158. Pimenta - Lindl. - [Myrtaceae],
159. Pinaropappus - Less. - [Asteraceae],
160. Piper - L. - [Piperaceae],
161. Piqueria - Cav. - [Asteraceae],
162. Pisonia - L. - [Nyctaginaceae],
163. Pithecellobium - Mart. - [Fabaceae],
164. Plantago - L. - [Plantaginaceae],
165. Pleopeltis - Humb. & Bonpl. ex Willd. - [Polypodiaceae (Polypodioid)],
166. Pluchea - Cass. - [Asteraceae],
167. Plumbago - L. - [Plumbaginaceae],
168. Plumeria - L. - [Apocynaceae],
169. Poiretia - Vent. - [Fabaceae],
170. Polianthes - L. - [Agavaceae],
171. Polygala - L. - [Polygalaceae],
172. Polygonum - L. - [Polygonaceae],
173. Porophyllum - Adans. - [Asteraceae],
174. Portulaca - L. - [Portulacaceae],
175. Pouteria - Aubl. - [Sapotaceae],
176. Prosopis - L. - [Fabaceae],
177. Prunus - L. - [Rosaceae],
178. Psidium - L. - [Myrtaceae],
179. Psittacanthus - Mart. - [Loranthaceae],
180. Psoralea - L. - [Fabaceae],
181. Pteridium - Gled. ex Scop. - [Dennstaedtiaceae],
182. Punica - L. - [Lythraceae (Punicaceae)],
183. Quassia - L. - [Simaroubaceae],
184. Quercus - L. - [Fagaceae],
185. Randia - L. - [Rubiaceae],
186. Ranunculus - L. - [Ranunculaceae],
187. Ricinus - L. - [Euphorbiaceae],
188. Rivina - L. - [Phytolaccaceae],
189. Rosa - L. - [Rosaceae],
190. Rosmarinus - L. - [Lamiaceae],
191. Rubus - L. - [Rosaceae],
192. Rumex - L. - [Polygonaceae],
193. Russelia - Jacq. - [Scrophulariaceae (now placed in Plantaginaceae)],
194. Ruta - L. - [Rutaceae],
195. Salvia - L. - [Lamiaceae],
196. Sambucus - L. - [Caprifoliaceae],
197. Sanvitalia - Lam. - [Asteraceae],
198. Satureja - L. - [Lamiaceae],
199. Schinus - L. - [Anacardiaceae],
200. Schkuhria - Roth - [Asteraceae],
201. Sclerocarpus - Jacq. - [Asteraceae],
202. Sedum - L. - [Crassulaceae],
203. Selaginella - P.Beauv. - [Selaginellaceae],
204. Senna - Mill. - [Fabaceae],
205. Serjania - Mill. - [Sapindaceae],
206. Sida - L. - [Malvaceae],
207. Smilax - L. - [Smilacaceae],
208. Solanum - L. - [Solanaceae],
209. Sonchus - L. - [Asteraceae],
210. Spondias - L. - [Anacardiaceae],
211. Stachytarpheta - Vahl - [Verbenaceae],
212. Stemmadenia - Benth. - [Apocynaceae],
213. Stenocereus - (A.Berger) Riccob. - [Cactaceae],
214. Syzygium - Gaertn. - [Myrtaceae],
215. Tagetes - L. - [Asteraceae],
216. Tamarindus - L. - [Fabaceae],
217. Tanacetum - L. - [Asteraceae],
218. Tecoma - Juss. - [Bignoniaceae],
219. Teloxys - Moq. - [Chenopodiaceae (now placed in Amaranthaceae)],
220. Ternstroemia - Mutis ex L.f. - [Theaceae],
221. Theobroma - L. - [Sterculiaceae (now placed in Malvaceae)],
222. Thevetia - L. - [Apocynaceae],
223. Tilia - L. - [Tiliaceae (now placed in Malvaceae)],
224. Tournefortia - L. - [Boraginaceae],
225. Trichilia - P.Browne - [Meliaceae],
226. Tridax - L. - [Asteraceae],
227. Tropaeolum - L. - [Tropaeolaceae],
228. Turnera - L. - [Turneraceae],
229. Urtica - L. - [Urticaceae],
230. Valeriana - L. - [Valerianaceae],
231. Verbena - L. - [Verbenaceae],
232. Verbesina - L. - [Asteraceae],
233. Viola - L. - [Violaceae],
234. Vitex - L. - [Verbenaceae (now placed in Lamiaceae)],
235. Vitis - L. - [Vitaceae (Vitidaceae)],
236. Waltheria - L. - [Sterculiaceae (now placed in Malvaceae)],
237. Xanthosoma - Schott - [Araceae],
238. Zea - L. - [Poaceae].
* Although not totally comprehensive, this should be a fairly representive sample of medicinal genera used in Morelos, Mexico.

Also provided is a supportive appendix to this summary.

References

Atlas de las Plantas de la Medicina Tradicional Mexicana
http://www.medicinatradicionalmexicana.unam.mx/
Cited as: Atlas Mexico, Guerrero, Hidalgo, Michoacán, Morelos, Oaxaca, Puebla, Quintana Roo, San Luis Potos�, Sonora, Tabasco, Veracruz, Yucatán. If cited "(Atlas Mexico)," this indicates medicinal use in Mexico. If cited "(Atlas Mexico: Morelos)," this indicates medicinal use in Morelos within Mexico. See reference for additional information.

Editor (1885) Materia Medica of the new Mexican Pharmacopoeia, Part 1,
American Journal of Pharmacy, Vol. 57, #5, pgs. 3-6.
Cited as: AJP1885-Mexico-1.

Editor (1885) Materia Medica of the new Mexican Pharmacopoeia, Part 2,
American Journal of Pharmacy, Vol. 57, #6, pgs. 10-12.
Cited as: AJP1885-Mexico-2.

Editor (1885) Materia Medica of the new Mexican Pharmacopoeia, Part 3,
American Journal of Pharmacy, Vol. 57, #7, pgs. 5-8.
Cited as: AJP1885-Mexico-3.

Editor (1885) Materia Medica of the new Mexican Pharmacopoeia, Part 4,
American Journal of Pharmacy, Vol. 57, #8, pgs. 4-7.
Cited as: AJP1885-Mexico-4.

Editor (1885) Materia Medica of the new Mexican Pharmacopoeia, Part 5,
American Journal of Pharmacy, Vol. 57, #9, pgs. 3-7.
Cited as: AJP1885-Mexico-5.

Editor (1885) Materia Medica of the new Mexican Pharmacopoeia, Part 6,
American Journal of Pharmacy, Vol. 57, #10, pgs. 5-6.
Cited as: AJP1885-Mexico-6.

Editor (1885) Materia Medica of the new Mexican Pharmacopoeia, Part 7,
American Journal of Pharmacy, Vol. 57, #11, pgs. 6-9.
Cited as: AJP1885-Mexico-7.

Editor (1885) Materia Medica of the new Mexican Pharmacopoeia, Part 8,
American Journal of Pharmacy, Vol. 57, #12, pgs. 3-6.
Cited as: AJP1885-Mexico-8.

Angiosperm Phylogeny Group (1998) An ordinal classification for the families of flowering plants, Annals of the Missouri Botanical Garden 85:531-553.
Angiosperm Phylogeny Group II (2003) An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II, Botanical Journal of the Linnean Society 141:399-436.
Cited as: APG II.
Angiosperm Phylogeny Group (2009) An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III, Botanical Journal of the Linnean Society 161 (2): 105-121.
Cited as: APG III.
Chase, M. W., Christenhusz, M. J. M., Fay, M. F., Byng, J. W., Judd, W. S., Soltis, D. E., ... & Stevens, P. F. (2016) An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG IV. Botanical Journal of the Linnean Society, 181(1), 1-20.
Cited as: APG IV.

Atlas de las Plantas de la Medicina Tradicional Mexicana
http://www.medicinatradicionalmexicana.unam.mx/atlas.php
http://www.medicinatradicionalmexicana.unam.mx/
Cited as: Atlas Mexico,

American Botanical Council
http://www.herbalgram.org/youngliving/herbalgram/
Cited as: Herbalgram.

Most of the scientific names for family, genus, species, variety, and subspecies listed in this dictionary are consistent with those provided in the work of John Kartesz and the Biota of North America Program (http://www.csdl.tamu.edu/FLORA/b98/check98.htm).
This is cited as:
BONAP or U.S.A.
When this citation appears, it can be assumed that the plants involved are naturalized or native in the U.S.A. or North America north of Mexico.
A scientific name, including author(s) and followed by the identifiers "Family Name, Genus Name, Species Name, Variety Name, or Subspecies Name" can be assumed to be consistent with a preferred name as listed by BONAP. If a name is not the same as that preferred or accepted by BONAP, additional comments on the reasons for this are made.
For plants in New Mexico, some synonyms (alternative scientific names) are included according to BONAP. When common names or synonyms for scientific names are derived from this work, this is also indicated by the citation BONAP.
For an additional sources of currently accepted scientific names and their synonyms, see:

Britton & Brown (1913) An Illustrated Flora of the Northern United States and Canada, 2nd Edition is cited as: northern U.S.A.
See Medicinal Plant excerpts from Michael Moore:
http://www.swsbm.com/Britton-Brown/Britton-Brown1.html
http://www.swsbm.com/Britton-Brown/Britton-Brown2.html
http://www.swsbm.com/Britton-Brown/Britton-Brown3.html

Robert A. Bye, Jr. and Edelmira Linares (1986) Ethnobotanical Notes from the Valley of San Luis, Colorado, J. Ethnobiol. 6(2):289-306.
Cited as Bye & Linares (1986), Lower Rio Grande

Information on wild California plants:
Cited as: Calflora.
http://www.calflora.org/

Cantino, Philip D., James A. Doyle, Sean W. Graham, Walter S. Judd, Richard G. Olmstead, Douglas E. Soltis, Pamela S. Soltis & Michael J. Donoghue (2007) Towards a phylogenetic nomenclature of Tracheophyta, Taxon 56 (3) E1-E44.
Cited as: Cantino.

Umberto Quattrocchi, F.L.S. (2012) CRC World Dictionary of Medicinal and Poisonous Plants: Common Names, Scientific Names, Eponyms, Synonyms, and Etymology, CRC Press Taylor & Francis Group.
Cited: Quattrocchi

Curtin, L.S.M. (1965) Healing herbs of the upper Rio Grande. Cited as: Upper Rio Grande Valley.

Joie Davidow (1999) Infusions of Healing.
Cited as: Maya, Mexican-American, and Nahuatl.

EncicloVida
http://www.enciclovida.mx/
http://enciclovida.mx/especies/6020835
Cited EncicloVida.

Department of Agriculture Ethnobotany Database (mostly uses of medicinal plants)
http://hpm101.gotadsl.co.uk/perl/ace3/searches/browser/EthnobotDB
http://ukcrop.net/perl/ace/search/EthnobotDB
Cited as: EthnobotDB.

The Families of Flowering Plants
L. Watson and M. J. Dallwitz
http://www.biologie.uni-hamburg.de/b-online/delta/angio/
Cited as: Delta.

Gonz�les-Elizondo M., L�pez-Enrique L., Gonz�lez-Elizondo S., Tenla-Flores J. (2004) Plantas Medicinales del Estado de Durango y zonas aleda�as, Direcci�n de publicaciones del Instituto Polit�cnico Nacional, M�xico.
Martha Gonz�lez Elizondo, I. Lorena L�pez Enriquez, M. Socorro Gonz�lez Elizondo, Jorge A. Tena Flores (2004) Plantas medicinales del estado de Durango y zonas aleda�as, CIIDIR Durango, Instituto Politecnico Nacional, M�xico.
Cited as: Durango Mexico.

Elsa Campos is a curandera that knows plants from Morelos, Mexico.
Cited as: Elsa Campos.

EOL

Flora of North America @ efloras.org.htm
Cited as: FNA.

Ford, K.C. (1975) Las Yerbas de la Gente: A Study of Hispano-American Medicinal Plants, University of Michigan, Anthropological Papers no. 60, Ann Arbor.

Global Compositae Checklist is a searchable integrated database of nomenclatural and taxonomic information for the family Asteraceae.
http://compositae.landcareresearch.co.nz/
Cited as: TICA.

Global Invasive Species Database
http://www.issg.org/database/welcome
Cited as Spanish, English, English-Canada, English-United Kingdom.

Roalson and Allred (1995) A Working Index of New Mexico Vascular Plant Names, New Mexico Agr. Exp. Sta. Res. Rep. 702.
Kelly W. Allred (2010) Flora Neomexicana I:
The Vascular Plants of New Mexico,
An Annotated Checklist to the Names of Vascular Plants, with Synonymy and Bibliography, Downloadable Version, Range Science Herbarium, Department of Animal & Range Sciences, New Mexico State University, Las Cruces, New Mexico
(allred2010_flora_neomexicana_1_prelim.pdf).
See also Kelly Allred (2012) Flora Neomexicana. Vol. I: Annotated Checklist, 2nd Edition.
Cited as: NM.

International, when cited, applies to a name used by many countries.

The International Plant Names Index.
http://www.ipni.org/index.html
http://www.ipni.org/ipni/plantsearch?request_type=search&output_format=query&ret_defaults=on
Cited as: IPNI.

For plant names in Canada, Mexico, and United States, access Integrated Taxonomic Information System. Cited ITIS.
http://www.cbif.gc.ca/pls/itisca/taxaget?p_ifx=plglt
http://annual.sp2000.org/show_database_details.php?database_name=ITIS
Cited as: ITIS.

International Union for Conservation of Nature and Natural Resources (IUCN) or World Conservation Union
The latest update is the 2006 Red List, released on 4 May 2006.
IUCN Red List of Threatened Species (also known as the "IUCN Red List" and "Red Data List")
http://www.iucnredlist.org/
Cited as: IUCN.

The Jepson Herbarium
University of California, Berkeley
http://ucjeps.berkeley.edu/IJM.html
Cited as: Jepson

Charles W. Kane (2006) Herbal Medicine of the American Southwest. Lincoln Town Press. Tucson, Arizona. Cited as: American Southwest.

Kay, M. A. (1996) Healing with plants in the American and Mexican West.
Cited as: Aztec, Baja California, Baja California Norte, Baja California Sur, Californian Spanish, Colorado Spanish, Mexico Spanish, New Mexico Spanish, Northwestern New Spain, or Kay.

Vascular Plant Families and Genera
http://www.kew.org/data/genlist.html
Cited as: KEW.
Also, includes The Plant List
http://www.theplantlist.org/

Mabberley, D.J. (1997) The plant-book, a portable dictionary of vascular plants, second edition, Cambridge University Press. Reprinted with correction 1998, 2000, 2002.
Cited as: Plant Book.

Mansfeld's Encyclopedia of Agricultural and Horticultural Crops (P. Hanelt & IPK (eds.) 2001, Springer), electronic version: IPK Gatersleben.
Also Mansfeld's Encyclopedia of Agricultural and Horticultural Crops (Except Ornamentals), Springer-Verlag, Berlin, Heidelberg, New York.
Cited as: Mansfeld's Encyclopedia, Mansfeld's Encyclopedia-Guatemala, Mansfeld's Encyclopedia-Mexico, Mansfeld's Encyclopedia-Yucatán.

Plantas que curan is a collection of articles on Mexican medicinal plants that was featured in one of Mexico's most respected and popular tourism magazines: M�xico Desconocido (Unknown Mexico).
Some of this material was presented in web pages by M�xico desconocido.
Cited as: En Nahuatl or M�xico Desconocido.

Mills, Simon Y. (1988) The Dictionary of Modern Herbalism, Healing Arts Press.
Mills, Simon Y. (1991) Out of the Earth, Viking Arkana.
Cited as: European English.

Multilingual Multiscript Plant Name Database
This site (http://www.plantnames.unimelb.edu.au/Sorting/List_bot.html)
from the University of Melbourne provides a tool that gives plant names in different languages.
Cited as: MMPND, MMPND-English, or MMPND-Spanish, English, or Spanish.

Moerman, D. 2011. Native American Ethnobotany, now http://naeb.brit.org/.
Cited as: Moerman.

Michael Moore's published works. See also Plant Images by Common English and North American Spanish Name (http://www.swsbm.com/homepage/NameIndex.html).
Cited as: Moore.

Nabhan, G., S. Buckley, and H. Dial (2015) Pollinator Plants of the Desert Southwest: Native Milkweeds (Asclepias spp.). USDA-Natural Resources Conservation Service, Tucson Plant Materials Center, Tucson, AZ. TN-PM-16-1-AZ.

Native American Ethnobotany Database
Foods, Drugs, Dyes, and Fibers of Native North American Peoples.
Materials provided by Dan Moerman, Professor of Anthropology.
http://www.umd.umich.edu/cgi-bin/herb/
Cited as: NAEDB.

Pacific Island Ecosystems at Risk project
Cited as: PIER

Jose Ortiz y Pino III (1972) The herbs of Galisteo and their powers, Galisteo historic museum.
Cited as: Galisteo

Plants For A Future: Database Search.
Cited as: PFAF, Southwestern N. America/Mexico.

Plant list
http://www.theplantlist.org/
Cited as: Plant List

PlantSystematics.org
http://132.236.163.181/index.html
Cited as: PSORG.

Ratsch, C. (2005) Encyclopedia of Psycho-active Plants, Park Street Press.
Cited as: C. Ratsch.

Sievers, A.F. (1930) The Herb Hunters Guide. Misc. Publ. No. 77. USDA, Washington DC.

Smith, Alan R., Kathleen M. Pryer, Eric Schuettpelz, Petra Korall, Harald Schneider & Paul G. Wolf (2006) A classification for extant ferns, Taxon 55 (3) 705-731.

Center for Sonoran Desert Studies
http://www.desertmuseum.org/center/
http://www.desertmuseum.org/programs/nomenclature/
South of Yécora, focused on Alamos.
Cited as: southern Sonora.

Botanical nomenclature of the Américas:
http://www.fundaciondoctordepando.com/GLOSARIOS%20y%20VOCABULARIOS/Nomenclatura%20Bot%E1nica-INTRODUCCI%D3N.htm
http://www.fundaciondoctordepando.com/Index.htm
http://www.fundaciondoctordepando.com/GLOSARIOS y VOCABULARIOS/Nomenclatura Bot%E1nica-Spanish-Américas.htm
http://www.diccionariosdigitales.com/
http://www.fundaciondoctordepando.com/
Fundaci�n Doctor Pando. Glosario.
For names starting with the letter "A" try
http://www.fundaciondoctordepando.com/GLOSARIOS%20y%20VOCABULARIOS/Nomenclatura%20Bot%E1nica-AAA.htm
This work includes Spanish names of native New World plants, as well as Spanish names of some plants native to Old World, possibly introduced to New World.
Cited as: Spanish-Américas.

Stevens, P.F. (2001 onwards) Angiosperm Phylogeny Website.
http://www.mobot.org/MOBOT/research/APweb/.
Cited as: APweb.

Tropicos
http://www.tropicos.org/Home.aspx
Cited as: Tropicos, Chiapas, Honduras.

UNEP (2004) Secretariat for the Conservation of Biological Diversity, Conference of Parties, Decision VI/9
Global Strategy for Plant Conservation.
http://www.biodiv.org/decisions/default.asp?dec=VI/9.
Home: http://www.biodiv.org/default.shtml
2006 Catalogue of Life: http://annual.sp2000.org/search.php
The Global Biodiversity Information Facility (GBIF): http://www.asia.gbif.net/portal/index.jsp
Cited as: UNEP.

Uphuf, J. C. Th. (1959) Dictionary of Economic Plants, New York.
Cited as: Uphuf, 1959

USDA, NRCS. 2006. The PLANTS Database (http://plants.usda.gov, 3 July 2006). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.
http://plants.usda.gov/index.html
Cited as: USDA.

Richard C. White (2003) Elsevier's dictionary of plant names of North America including Mexico, Elsevier.
Cited as: southwest US & northern Mexico.
This dictionary by Richard White contains scientific names and common names in Spanish and English for the most important plant species mainly in the southwestern United States and northern Mexico.

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