The purpose of naming organisms is to provide a means of reference to facilitate communication about those organisms. A universally understood, precise, and stable system of naming is essential for effective scientific communication. A simple system of naming is also desirable, but simplicity and precision are unfortunately not always compatible.

Humans around the world have been naming plants, and probably fungi and algae too, for millennia. A culture that utilizes these organisms for food, medicine, wood, fibre, mind alteration, etc., needs a means of referring to particular organisms, and common names (also called vernacular names) probably exist in every language.

Many of these common names refer to some physical aspect of the plant. The name bluebell derives from blue, bell-shaped flowers. The name cuckoo pint derives not from the bird and a unit of capacity, but from Old English cuic and pintel, meaning “lively” (quick) and “penis”, respectively, referring to the erect, cylindric, fleshy appendix of the inflorescence. Sometimes plant uses are the basis of the name, e.g. medicine in self-heal and woundwort; parasite-control in fleabane; bedding material in bedstraw. Frequently folk taxonomy is also implicit in the name, and this may coincide with a modern scientific classification of a group, e.g. trees and shrubs named as various kinds of oak or Eiche in English and German, respectively, are scientifically named Quercus, thus durmast oak or Traubeneiche is Q. petraea; holm oak or Steineiche is Q. ilex; white oak or Flaumeiche is Q. pubescens (in Europe, whereas the North American white oak is Q. alba). However, the name oak can be used for phylogenetically quite unrelated plants, e.g. poison oak in western North America is Toxicodendron diversilobum, which is not closely related to Quercus. Similarly, white bryony and black bryony in Britain are, respectively, Bryonia cretica and Dioscorea communis (or Tamus communis); both are climbing, non-woody vines, but again they are not at all closely related.

There is, however, a problem with common names: while they may provide a popular “handle” for discussing organisms, they are frequently ambiguous, often with multiple names in common use for the same organism, and with several examples of the same name, in one or more languages, applied to different organisms in different geographical regions. In Britain, the name cuckoo-flower has been applied to seventeen species in ten families (Watts, 2000). One of those species probably has more British common names than any other plant, including lords-and-ladies, parson-in-the-pulpit, cuckoo-pint, and some names used only regionally, e.g. ram’s-horn (Sussex) and adder’s-tongue (Cornwall and Somerset). The name bluebell is applied to three quite different species in England, Scotland, and North America, and the Scottish bluebell is the harebell in England.

When the scientific naming of organisms was developing in the 16th to 18th centuries, the universal language of science was Latin. That is why the names use the Latin language. Greek-derived words are also used, and indeed words from many other languages, but they are all treated as being Latin. The basic principle is that scientific names, which are often called Latin names, are used worldwide, enabling scientists speaking different languages to communicate readily with one another. In the examples given above, the species that is variously called lords-and-ladies, parson-in-the-pulpit, cuckoo-flower, cuckoo-pint, ram’s-horn, and adder’s-tongue is Arum maculatum, not only in Britain but everywhere else in the world. English bluebell is everywhere Hyacinthoides non-scripta; North American bluebell is Mertensia virginica; Scottish bluebell and English harebell are Campanula rotundifolia; English toothwort and German Schuppenwurz are Lathraea squamaria; North American toothwort and English bittercress are species of Cardamine, and another species of English cuckoo-flower is Cardamine pratensis. In a global context, therefore, using common names can be ambiguous and highly confusing, whereas using scientific names enables more precise communication.

The current system of biological nomenclature dates back to the mid-18th-century, when Swedish naturalist Carolus Linnaeus (Carl von Linné) published his Species plantarum and Systema naturae (Linnaeus, 1753, 1758), in which a binomial, sometimes called binominal or binary, i.e. “two-name”, system was introduced. A binomial is the name of a species (where a species is considered to be the basic taxonomic unit comprising a group of individual organisms). A binomial consists of the name of a genus, e.g. Quercus, followed by what Linnaeus called a nomen triviale (trivial name), which is now called a specific epithet, e.g. robur, hence Quercus robur. This is a very user-friendly method for naming millions of species of organisms, because even if you know a species only by its name, you already know to which genus it belongs. It is much easier to remember the names and taxonomic placement of a relatively small number of genera than it is a very large number of species.

Taxonomy (or systematics) is the science that deals with circumscribing and classifying organisms in a system. Nomenclature is the provision of means of reference, i.e. names, for those organisms. Classifications are in a constant state of change as new data come to light, especially with regard to evolutionary relationships inferred from molecular studies. To pretend that any particular classification ought to be fixed as the final word on a group of organisms would be grossly unscientific. Because of the nature of the current nomenclatural system, this perpetual process of taxonomic reappraisal inevitably causes a certain degree of nomenclatural change. Changing a family to a subfamily results in a name change, e.g. Pyrolaceae becomes Pyroloideae. Moving a genus from one family to another does not result in a name change. Moving a species from one genus to another necessarily causes a name change because under the binomial system the accepted generic name is part of the species name, e.g. when the species originally described as Hyacinthus non-scriptus was moved from the genus Hyacinthus to the genus Hyacinthoides, its name had to be changed to Hyacinthoides non-scripta. Likewise moving a variety from one species to another causes a name change. Names below the rank of genus include an inherent classification: a species named Hyacinthoides non-scripta belongs to the genus Hyacinthoides, but a genus named Hyacinthoides can belong to any family, e.g. to Asparagaceae, Hyacinthaceae, or Liliaceae. This does not mean that nomenclature mandates a particular classification. Taxonomy and nomenclature are quite different things. The taxonomist uses evidence from research to arrive at a particular classification and then uses the rules of nomenclature to apply the correct name to the taxa recognized.

The purpose of having rules for biological nomenclature is to provide a stable method of naming organisms, avoiding and rejecting the use of names that may cause error, ambiguity, or confusion. The current rules for the scientific nomenclature of plants, as well as for fungi and algae, are contained in the International Code of Nomenclature for algae, fungi, and plants (Shenzhen Code; Turland & al., 2018). Unless otherwise qualified, “Code” in this guide refers to the Shenzhen Code. The title was formally changed at the XVIII International Botanical Congress in Melbourne in 2011, whereas previously it was the International Code of Botanical Nomenclature, or ICBN. The acronym “ICN”, standing for “International Code of Nomenclature”, is best avoided because it could refer to any one of five biological codes, of which more below. Note that the current edition of the Code supersedes all previous editions. Using a previous edition is therefore very risky because you could follow rules that have been changed or fail to follow new rules.

The Code governs the nomenclature of all organisms traditionally treated as algae, fungi, or plants, whether fossil or non-fossil, including blue-green algae (Cyanobacteria), chytrids, oomycetes, slime moulds, and photosynthetic protists with their taxonomically related non-photosynthetic groups (but excluding Microsporidia). The nomenclature of hybrids is also covered, but that of cultivated plants is dealt with separately by the International Code of Nomenclature for Cultivated Plants (ICNCP or Cultivated Plant Code), prepared under the authority of the International Commission for the Nomenclature of Cultivated Plants and now in its 9th edition (Brickell & al., 2016). Three additional codes govern the nomenclature of animals, prokaryotes (bacteria etc.), and viruses. They are, respectively, the International Code of Zoological Nomenclature (ICZN or Zoological Code; International Commission on Zoological Nomenclature, 1999); the International Code of Nomenclature of Prokaryotes (Parker & al., 2019); and the International Code of Virus Classification and Nomenclature (International Committee on Taxonomy of Viruses, 2018).

Unlike most modern sciences, e.g. ecology, the nomenclature of algae, fungi, and plants still makes full use of literature dating back to 1753, and in this respect it seems more like history than science. This strong historical element persists because the rules of the Code, except where expressly limited, are retroactive to 1753. Retroactive means that they function as if they had been in the Code in 1753, and indeed as if the Code had existed in 1753. In reality, the Code did not exist until Alphonse de Candolle published his Lois de la Nomenclature Botanique in 1867 (Candolle, 1867), and much of the content of the Code today was added since 1867.

Novice and veteran users of the Code alike would agree that it is a very complex document. This complexity has evolved over 17 editions beginning with Candolle’s Lois. Throughout this more than 150-year history, diverse issues have arisen prompting scientists to refine the rules every few years at an International Botanical Congress, and since 2018 also at an International Mycological Congress, each time making the Code a little more precise but at the same time a little more complex. Some rules are of fundamental importance, whereas others exist only to govern rare cases. The fundamental rules are sometimes quite simple, whereas the rare-case ones are sometimes formidably complex, and vice versa. It is not necessary to learn and understand every rule in the Code in order achieve competence in nomenclature. This guide aims to highlight the most important rules.

The rules of the Code are not law but are voluntarily followed with an international consensus, i.e. the majority of botanists, mycologists, and phycologists worldwide have agreed to follow the rules. Scientific names published in compliance with these rules can achieve international acceptance. Names published under alternative sets of rules might gain acceptance among the particular groups of scientists who follow those particular rules, but they will not be generally accepted by the international scientific community.

Over the last few decades, efforts have been made to harmonize the terminology and rules of the current separate biological codes into a single set of rules for biological nomenclature, which came to be called the Draft BioCode (Greuter & al., 1998, 2011). The current codes, while they have a great deal in common, have quite different rules for some situations. For example, the Code for algae, fungi, and plants rules that a tautonym, in which the specific epithet exactly repeats the generic name, cannot be validly published, whereas tautonyms such as Glis glis and Rattus rattus are permitted by the ICZN. There is also a problem with homonyms, i.e. two or more names spelled exactly alike but applying (usually) to different organisms. While a later (or junior) homonym cannot be legitimate under the Code for algae, fungi, and plants, or potentially valid under the ICZN, these rules apply mostly within their respective codes, rarely across them, so that, e.g., Pieris applying to a woody plant and Pieris applying to a butterfly are both legitimate/potentially valid names. There is also a problem with terminology between the codes, in which different terms are used for the same concept and the same term is used for different concepts. This is illustrated by the examples in Table 1 (p. 14).

The Draft BioCode, developed by the International Committee on Bionomenclature (http://www.bionomenclature.net/), was intended to solve these problems through its eventual adoption by the various disciplines of the biological community. The relative simplicity of the Draft BioCode derived from its dealing only with the names of the present and future; it did not attempt to rule on the nomenclature of the past ca. 250 years. Because of this, it could only be implemented effectively after the separate codes had agreed to introduce mandatory registration of new names and to adopt lists of protected names (called “Names in Current Use” [NCU] lists). However, enthusiasm for the Draft BioCode was significantly lacking in at least the botanical and zoological communities, such that, in 2012, the International Committee on Bionomenclature decided not seek its implementation but rather to use it as a framework for facilitating communication between the different biological disciplines and nomenclatural codes, and to maintain its availability should it be required at some future date. For a discussion of the challenges facing the codes of biological nomenclature see Knapp & al. (2004).

Table 1.Download as CSV 

Comparison of terms used for three statuses of names across five codes of biological nomenclature (for additional terms, and for those recommended for use in biological nomenclature, see David & al., 2012).

International Code of
Nomenclature for algae, fungi, and plants	Zoological Nomenclature	Nomenclature of Prokaryotes	Virus Classification and Nomenclature	Nomenclature for Cultivated Plants
validly published	available	validly published	established	established
legitimate	potentially valid	legitimate	valid	acceptable
correct	valid	correct	accepted	accepted

One of the criticisms aimed at the Code today is that modern phylogenetics are incompatible with a “Linnaean”, rank-based, hierarchical system of nomenclature, although it has been argued that there is no inherent obstacle to naming clades under the Code for algae, fungi, and plants (Barkley & al., 2004). An alternative system has been under development in recent years, namely the International Code of Phylogenetic Nomenclature or PhyloCode (Cantino & Queiroz, 2010), which provides rules for naming all clades of organisms, whether extant or extinct. The PhyloCode may be used concurrently with what it calls the “rank-based codes”, i.e. the four traditional codes for algae/fungi/plants, animals, prokaryotes, and viruses. The PhyloCode relies on the rank-based codes to determine the acceptability of pre-existing names, but it governs the application of those names independently. It is still a draft, under revision, and will take effect, non-retroactively upon publication of Phylonyms: a Companion to the PhyloCode.

The following methods of disseminating information do not constitute effective publication, with some rules taking effect only after certain dates:

It is important to know the date of effective publication whenever names or other nomenclatural acts, such as designations of type, are competing for priority. When two competing names were published in the same year, the exact date is needed. Article 31.1 rules on how to determine the date of effective publication. Put simply, it is the date on which the printed matter or electronic material became available as defined in Art. 29 and 30. Electronic material becomes available as soon as it is accessible electronically via the World Wide Web. But at what point does printed matter become available? Recommendation 31A helps here by advising that the date on which the publisher or publisher’s agent delivers printed matter to one of the usual carriers for distribution to the public should be accepted as its date of effective publication.

For many older works, Taxonomic literature, ed. 2 (TL-2; see pp. 151 and 154) is a very important source of meticulously researched information on dates of effective publication. The dates given by TL-2 often differ from what is printed on the title pages of the books. Sometimes the title-page date represents the completion of a multi-part work, whereas the individual parts were published on different, earlier dates. Sometimes a title-page date is simply wrong. Sometimes there is no evidence beyond the date that appears in the printed matter or electronic material, and in that case that date must be accepted as correct (Art. 31.1).

Be careful when determining the dates of papers in journals. Firstly, when separately issued parts of a journal volume have been bound together, you should not trust the date that appears on the cover, because it could be a book-binder’s error. Instead look at the individual front and back covers of the relevant separate part, if the covers have been retained upon binding; or sometimes the date may be on the title page(s), preliminary pages, or the first or last text pages of the part. Some journals issue separate covers and title pages for the whole volume and for each part, with a later date appearing on those for the whole volume. Sometimes a volume may have been issued in parts without covers or title pages. There may be a list of page ranges with corresponding dates on one of the preliminary pages of the volume, or dates may be printed on the first or last page of each part, in which case you have to search for them. Some journals print the date of publication of a particular part not in that part but in the following part.

For electronic material, look for a statement of date in the text of the PDF document itself; only if no date is given there should you look on the web page(s) from which the document is served. Bear in mind that the date given on the web page could be, e.g., the general date of an issue of a journal, not of the individual papers therein. Do not use the “created” or “modified” dates in the “document properties” (i.e. the metadata); the document may have been issued online days after its creation or last modification, or these dates could merely reflect the date of your download.

If a publication exists in parallel printed and electronic versions, do not assume they were necessarily published simultaneously. Look for evidence of date for both versions. If there is no evidence that they were published on different dates, they must be treated as effectively published on the same date (Art. 31.2).

Suppose you wish to publish the name of a new taxon. What do you need to do in order for it to be validly published? The main requirements to remember are itemized below and illustrated by Figs 2, 3, and 4 (pp. 32–36; while Figs 5 and 6, pp. 37–38 show historical protologues for comparison).

• The name must be effectively published (Art. 32.1(a)), as explained in Chapter 4.
• The name must have a form that complies with Art. 16–27 (Art. 32.1(c)). See Rules on the formation of names, pp. 48–54.
• For the name of a taxon below the rank of genus, the name of the genus or species to which it is assigned must be validly published either previously or at the same time (Art. 35.1).
• The protologue must include either a description or a diagnosis that is in either Latin or English (Art. 38.1(a) and 39.2). Optionally, you may include both a description and a diagnosis, and you may provide an additional description and/or diagnosis in a language other than Latin or English; such optional additions are not prohibited by the Code and will not affect valid publication, although editors of journals and books may have their own guidelines on what you can include. A description gives the physical properties of the taxon, e.g. morphology, colour, odour, flowering time, chromosomes, chemical properties, or DNA sequence data. A diagnosis of a taxon is a statement of that which distinguishes the taxon from other taxa in the opinion of the author of the taxon (Art. 38.2).
• For the name of taxon at the rank of genus or below, you must designate the type of the name in the protologue (Art. 40.1), using the word “typus” or “holotypus”, or its abbreviation (e.g. holo.), or its equivalent in a modern language (e.g. holotipo, holotype, tipo, type) (Art. 40.6).
• For the name of a species or infraspecific taxon, you must designate a specimen (Art. 40.4) as the holotype, although for non-fossil microscopic algae and non-fossil microfungi an effectively published illustration is permitted as the holotype under certain circumstances (see Art. 40.5).
• For the name of a species or infraspecific taxon, when the holotype is a specimen (which it almost always will be), you must specify in the protologue the single herbarium, collection, or institution in which it is conserved (Art. 40.7).
• Additional, special rules exist for the names of algae (Art. 40.8 and 44), fungi (Art. 40.8 and F.5), fossils (Art. 43), and hybrids (Chapter H), for which see Chapter 11.

Figure 2.

Three modern protologues of names of new plant taxa: Zyrphelis ecklonis subsp. oligocephala Zinnecker and Zyrphelis ecklonis subsp. strictifolia Zinnecker, from a paper in volume 60 of the journal Taxon by Ortiz & Zinnecker-Wiegand (2011: 1196), and Merianthera bullata R. Goldenb., Fraga & A.P. Fontana, from a paper in volume 61 of Taxon by Goldenberg & al. (2012: 1047). Reproduced by permission of the International Association for Plant Taxonomy. Components of the protologues are as follows:

• Names cited in full (generic name not abbreviated), authorship explicitly cited, and novel status indicated (“subsp. nov.” or “sp. nov.”); all three items are best practice and should certainly be followed (even if strictly they are not requirements for valid publication under the Code).
• Latin validating description or diagnosis for the names in Zyrphelis (here diagnoses), as required for names published between 1935 and 2011, inclusive (Art. 39.1).
• Latin or English validating description or diagnosis for Merianthera bullata (here an English description), as required for names published from 2012 onward (Art. 39.2).
• Citation of type (Art. 40.1), which is a specimen (Art. 40.4), using one of the words “typus” or “holotypus”, or its abbreviation, or its modern-language equivalent (here both words in Latin or English; Art. 40.6), specifying the single herbarium where the type is conserved (BOL, S, or MBML; Art. 40.7), and citing a duplicate, i.e. an isotype, in the herbarium UPCB. The exclamation mark (!) placed after the herbarium code in the Zyrphelis protologues indicates that the cited specimen has been seen by the author(s). No meaning should be inferred from the absence of exclamation marks in the Merianthera protologue because the authors did not use exclamation marks at all in their paper.

Figure 3.

A modern protologue of the name of a new plant taxon: Orychophragmus violaceus var. odontopetalus Ling Wang & Chuan P. Yang, from a paper in volume 22 of the journal Novon by Wang & al. (2012: 110). Reproduced by permission of Missouri Botanical Garden Press. Components of the protologue are as follows:

• Name cited in full (generic name not abbreviated), authorship explicitly cited, and novel status indicated (“var. nov.”); all three items are best practice and should certainly be followed (even if strictly they are not requirements for valid publication under the Code).
• Citation of type (Art. 40.1), which is a specimen (X.J. Ma, L. Wang & C.P. Yang 09009; Art. 40.4), using one of the words “typus” or “holotypus”, or its abbreviation, or its modern-language equivalent (here both words in English; Art. 40.6), and specifying the single herbarium where it is conserved (NEFI; Art. 40.7).
• Latin or English validating description or diagnosis (here a Latin diagnosis and an English description), as required for names published from 2012 onward (Art. 39.2).
• Notes on habitat and distribution, IUCN Red List category, and citation of paratypes (Art. 9.7).

Figure 4.

A modern protologue of the name of a new fungal taxon: Halegrapha paulseniana Luch & Lücking, from a paper in volume 48 of the journal Willdenowia by Luch & Lücking (2018: 416). Reproduced by permission of the authors and the Botanischer Garten und Botanisches Museum Berlin. Components of the protologue are as follows:

• Name cited in full (generic name not abbreviated), authorship explicitly cited, and novel status indicated (“sp. nov.”); all three items are best practice and should certainly be followed (even if strictly they are not requirements for valid publication under the Code).
• Citation of the identifier issued for the name by a recognized repository (“MycoBank MB 828103”), as required for new names of fungi published from 2013 onward (Art. F.5.1).
• Citation of type (Art. 40.1), which is a specimen (R. Lücking, B. Moncada & P. Bily 35834; Art. 40.4), using one of the words “typus” or “holotypus”, its abbreviation, or its modern-language equivalent (here in English, “holotype”; Art. 40.6), specifying the single herbarium where it is conserved (BISH; Art. 40.7), and citing two duplicates, i.e. isotypes, in the herbaria B and F. Additional collecting details of the type are also cited (locality with coordinates, altitude, habitat, and date).
• Latin or English validating description or diagnosis (here an English diagnosis; also an English description, not shown in this figure), as required for names published from 2012 onward (Art. 39.2).
• Also provided, but not shown in this figure, are remarks on the new species, including distribution, ecology, derivation of the specific epithet, and comparison with other taxa, as well as illustrations of the organism and its habitat.

Figure 5.

An 18th-century protologue of the name of a new fungal taxon: Phallus impudicus L. Part of page 1179 of volume 2 of the 1st edition of Linnaeus’s Species plantarum (Linnaeus, 1753: 1179). The components of the protologue are as follows:

• Sequential species number within the genus Phallus: “2.”
• Diagnostic phrase name (polynomial): “Phallus volvatus stipitatus, pileo celluloso.” (Phallus volvate, stipitate, with a cellular cap). This is Linnaeus’s nomen specificum legitimum (lawful specific name), in Latin, serving as the validating diagnosis of the species name.
• Specific epithet, in the margin: “impudicus.” (immodest). This is Linnaeus’s nomen triviale (trivial name), directly associated with the generic name (at the start of the phrase name and in the heading of the genus) to form the combination Phallus impudicus.
• Synonyms: five pre-starting-point phrase names are cited in synonymy; the illustration cited with the third synonym (Micheli, 1729: 201, t. 83) has been designated as the lectotype of P. impudicus (see Fig. 18, p. 77).
• Statement of provenance: “Habitat in Sylvis.” (It inhabits the woods).

Figure 6.

A 19th-century protologue of the name of a new plant taxon: Taraxacum glabrum DC. Part of page 147 of part 1 of volume 7 of Candolle’s Prodromus systematis naturalis regni vegetabilis (Candolle, 1838: 147). Components of the protologue are as follows, with abbreviations in the original Latin expanded here using square brackets:

• Sequential species number within the genus Taraxacum: “11.”
• Binomial: “T[araxacum]. glabrum” (specific epithet: glabrous).
• Validating diagnosis, in Latin: “T[araxacum]. glabrum, ex omni parte glaberrimum […] rostro abbreviato.” (Taraxacum glabrum, in every part very glabrous […] with beak shortened).
• Symbol meaning perennial: “♃”.
• Statement of provenance and collector’s name: “in humidis montanis Dahuriae ad Nuchu-Doban legit cl[arissimo]. Turczaninow.” (in damp montane [places] of Dahuria at Nuchu-Doban gathered by the most illustrious Turczaninow).
• Unpublished synonyms cited from Candolle’s correspondence with Turczaninow: “Hieracium glabrum, et postea Leontodon nov[a]. sp[ecies]. Turcz[aninow]. ! in litt[eris].” (Hieracium glabrum, and afterwards Leontodon new species. Turczaninow ! [I have seen] in letters/correspondence).
• Comparison with a supposedly related species: “Affine T. glaucantho, sed […]” (Akin to T. glaucanthum, but …).
• Indication that a specimen has been seen by Candolle: “(v[idi]. s[iccam]. comm[unicatam]. à cl[arissimo]. inv[entore].)” (I have seen a dry [plant, i.e. specimen] communicated by the most illustrious discoverer [i.e. Turczaninow]).

Suppose you wish to rename a taxon that has been named previously. You wish to publish a new combination, a name at new rank, or a replacement name (see Chapter 2 for definitions of those terms). What do you need to do in order for such a new name to be validly published? The main requirements to remember are itemized below and illustrated by Fig. 7 (p. 40; while Fig. 8, p. 41 shows a historical protologue for comparison).

• The new name must be effectively published (Art. 32.1(a)), as explained in Chapter 4.
• The new name must have a form that complies with Art. 16–27 (Art. 32.1(c)). See Rules on the formation of names, pp. 48–54.
• For the new name of a taxon below the rank of genus, the name of the genus or species to which the taxon is assigned must be validly published either previously or at the same time (Art. 35.1).
• You must cite the basionym or replaced synonym in the protologue together with a full and direct reference to its author and place of valid publication, with page or plate reference and date (Art. 41.5). “Direct” means citing the actual author and place of publication, not a different publication that in turn refers to the actual one, while “full” means all necessary details. Page or plate reference means the page or pages on which the basionym or replaced synonym was validly published or on which the protologue appears, not the pagination of the whole publication unless it is coextensive with that of the protologue (Art. 41 Note 1). If the publication is unpaginated, cite the page number in square brackets, e.g. “[42]” or use another unambiguous method (e.g. generic name plus species number for Miller’s The gardeners dictionary; Miller, 1768). If you need to cite an online publication that is the final version (e.g. the “Version of Record”) but still has preliminary pagination, you can note its online status and cite the preliminary page number in square brackets. Some journals require the full and direct reference to be given in the format “Author(s) (year: page/plate number(s))”, with the full bibliographic details of the publication given in the references section. Such a reference is still full and direct, even though it is split between two places in the publication, and it therefore complies with Art. 41.5, but theCode explicitly recommends against this method (see Rec. 41A.1).

Figure 7.

Two modern new combinations and a replacement name: Polyalthia fruticosa (Jessup) B. Xue & R.M.K. Saunders, P. hispida B. Xue & R.M.K. Saunders, and P. johnsonii (F. Muell.) B. Xue & R.M.K. Saunders, all from a paper in volume 61 of the journal Taxon by Xue & al. (2012: 1034). Reproduced by permission of the International Association for Plant Taxonomy. Components of the protologues are as follows:

• Names cited in full (generic name not abbreviated), authorship explicitly cited, and novel status indicated (“comb. nov.” or “nom. nov.”); all three items are best practice and should certainly be followed (even if strictly they are not requirements for valid publication under the Code).
• Basionym or replaced synonym indicated (“ ≡ ” indicates homotypic synonymy) together with a full bibliographic reference to its place of valid publication, as required for names published from 1953 onward (Art. 41.5); the basionym or replaced synonym is also cited (indicated does not necessarily mean cited), as required for names published from 2007 onward (Art. 41.5). Instead of the symbol “ ≡ ”, the word “basionym”, or its abbreviation (e.g. “basio.”), or its equivalent in another language may be used.
• Citation of type: again, this is good practice, although the Code does not require it for valid publication of a new combination, name at new rank, or replacement name.

Figure 8.

A 19th-century new combination and a replacement name, both from page 315 of part 1 of Kuntze’s Revisio generum plantarum (Kuntze, 1891: 315). Each name was validly published with a reference to the basionym or replaced synonym (Art. 41.1), although it was not a full reference, which was not required until 1953 (Art. 41.5). Components of these two protologues are as follows, with abbreviations in the original Latin expanded here using square brackets:

Aster asteroides (DC.) Kuntze:

• Homotypic synonym: “A[ster]. Heterochaeta Bth.”, i.e. A. heterochaeta Benth. ex C.B. Clarke 1876, a replacement name for Heterochaeta asteroides DC. Aster heterochaeta was nomenclaturally superfluous when published, and is therefore illegitimate under Art. 52.1, because Clarke should have used A. asteroides instead.
• Basionym: “Heterochaeta asteroides DC.” 1836.
• New combination: “A[ster]. asterodes [sic!] OK.”, i.e. A. asteroides (DC.) Kuntze. Kuntze’s spelling of the epithet is correctable to the original spelling of the basionym (Art. 60.1 and 60.2).

Aster asae Kuntze:

• Replaced synonym: “Big[elowia]. paniculata Asa Gray non Aster p[aniculatus]. Lam.”, i.e. Bigelowia paniculata A. Gray 1873 non Aster paniculatus Lam. 1783 nec A. paniculatus Mill. 1768.
• Replacement name: “A[ster]. Asae OK.”, i.e. A. asae Kuntze.

The generic names Aster and Bigelowia are spelled out above the entries on the same page. Kuntze abbreviated his own name as “OK” (Otto Kuntze). Notice the obsolete practice of using an initial capital letter in epithets of species names when they are proper nouns (see Rec. 60F.1): “Heterochaeta”, a generic name in apposition (nominative), and “Asae”, the genitive of Asa.

Some rules on valid publication are limited by date, meaning that they apply on or after a particular date but do not apply before that date. When rules are not limited by date, they apply from the nomenclatural starting-point of the taxonomic group concerned (e.g. 1 May 1753 for Spermatophyta; see Art. 13.1 and F.1). The most commonly encountered rules are summarized here, arranged by the date upon which, under the current Code, they become effective. Additional rules and dates apply to the names of algae (Art. 44), fungi (Art. F.5), fossils (Art. 43), and hybrids (Chapter H), for which see Chapter 11.

The remaining requirements for valid publication, not yet discussed, concern the actual form of scientific names. Under these rules, valid publication of a name depends on its having the required form, unlike the rules on orthography and gender (see Chapter 10), which are independent of valid publication and permit correction of errors in spelling and grammar.

The core rule on valid publication is Art. 32.1, which requires a name to be composed only of letters of the Latin alphabet and to have a form that complies with the provisions of Art. 16–27. Those provisions apply to names of taxa at different ranks, and are organized in a descending sequence from taxa above the rank of family to infraspecific taxa. They are described below.

Names of suprageneric taxa

Names above the rank of family (Art. 16.1) may be either automatically typified names formed from the name of an included genus, such as Magnoliophyta (from Magnolia), Pinopsida (from Pinus), and Poales (from Poa), or descriptive names, such as Angiospermae, Fungi, Gymnospermae, Monocotyledones, Spermatophyta, and Tracheophyta. An automatically typified name is so called because it automatically has the same type as the name of the genus from which it is formed. These names are formed by adding a termination (ending) appropriate to the rank of the name (Art. 16.3 and 17.1; see Table 5, p. 51) to the stem of the genitive of the generic name, with the connecting vowel -o- if the termination begins with a consonant. For example, Magnoliophyta is formed from Magnoli- (the stem of Magnoliae, the genitive of Magnolia) plus the connecting vowel -o- plus -phyta (the termination for a division or phylum of algae or plants); Poales is formed from Po- (the stem of Poae, the genitive of Poa) plus -ales (the termination for an order).

The name of a family or a subdivision of a family is formed in the same way (see Table 3, p. 50) but with a different termination: -aceae for family, -oideae for subfamily, -eae for tribe, and -inae for subtribe (Art. 18.1, 19.1, and 19.3; see Table 5, p. 51).

Names of families or subdivisions of families cannot be descriptive names, except for those listed in Art. 18.5, the traditional family names, e.g. Compositae, for which Art. 18.6 permits the use of an alternative family name (nomen alternativum, nom. alt.) formed from a generic name, which provides the type. These names are listed in Table 4 (p. 50).

Table 3.Download as CSV 

Formation of automatically typified suprageneric names, using family names as an example (see Art. 18.1).

Generic name	Genitive singular	Stem	Family name (add -aceae)
Aextoxicon	Aextoxicou	Aextoxic-	Aextoxicaceae
Aster	Asteris	Aster-	Asteraceae
Capparis	Capparis / -os	Cappar-	Capparaceae
Cycas	Cycadis	Cycad-	Cycadaceae
Dryopteris	Dryopteridis / -os	Dryopterid-	Dryopteridaceae
Juglans	Juglandis	Jugland-	Juglandaceae
Lilium	Lilii	Lili-	Liliaceae
Magnolia	Magnoliae	Magnoli-	Magnoliaceae
Melastoma	Melastomatis / -os	Melastomat-	Melastomataceae
Pinus	Pini	Pin-	Pinaceae
Plantago	Plantaginis	Plantagin-	Plantaginaceae
Poa	Poae	Po-	Poaceae
Potamogeton	Potamogetonis / -os	Potamogeton-	Potamogetonaceae
Salix	Salicis	Salic-	Salicaceae
Smilax	Smilacis	Smilac-	Smilacaceae
Vitis	Vitis	Vit-	Vitaceae

Table 4.Download as CSV 

Traditional and alternative family names and their types.

Traditional family name	Alternative family name (nomen alternativum)	Type
Compositae	Asteraceae	Aster L.
Cruciferae	Brassicaceae	Brassica L.
Gramineae	Poaceae	Poa L.
Guttiferae	Clusiaceae	Clusia L.
Labiatae	Lamiaceae	Lamium L.
Leguminosae	Fabaceae	Faba Mill. [= Vicia L.]
Palmae	Arecaceae	Areca L.
Papilionaceae *	Fabaceae	Faba Mill.
Umbelliferae	Apiaceae	Apium L.
* Conserved (see Chapter 8) against Leguminosae when the Papilionaceae are treated as a family distinct from the remainder of the Leguminosae.

Table 5.Download as CSV 

Mandatory terminations (endings) of suprageneric names according to rank and organismal group.

Rank	Termination			Article
	Algae	Fungi	Plants
division or phylum	-phyta	-mycota	-phyta	16.3
subdivision or subphylum	-phytina	-mycotina	-phytina	16.3
class	-phyceae	-mycetes	-opsida	16.3
subclass	-phycidae	-mycetidae	-idae	16.3
order	-ales			17.1
suborder	-ineae			17.1
family	-aceae			18.1
subfamily	-oideae			19.1
tribe	-eae			19.3
subtribe	-inae			19.3

Note that when the Papilionaceae are regarded as a family distinct from the remainder of the Leguminosae, the name Papilionaceae is conserved (see Chapter 8) against Leguminosae; otherwise Leguminosae Juss. 1789 has priority over Papilionaceae Giseke 1792. In addition, Art. 19.8 permits the use of Papilionoideae as an alternative to Faboideae when the Papilionaceae are included in the Leguminosae as a subfamily.

The rank-denoting terminations prescribed in Art. 16–19 (and summarized in Art. 37.2 footnote) must be used, and at the ranks of phylum to subclass, inclusive, different terminations are used for names of algae, fungi, and plants (see Table 5, p. 51). If additional ranks not mentioned in Art. 16–19 are inserted, e.g. to allow naming of clades in a large phylogenetic tree, then it is not mandatory to use a particular termination for the names in those additional ranks.

Note that suprageneric names are treated as plural nouns, hence it is grammatically better to write “the Orchidaceae are” than “the Orchidaceae is”. They are also written with an initial capital letter. Whether or not they should be italicized is a matter of editorial style and tradition, not of nomenclature. The Code neither rules nor recommends on the matter, but consistently italicizes all scientific names under its jurisdiction. Note that for zoological names, the International Code of Zoological Nomenclature (Appendix B: Gen. Rec. 6) recommends against italicizing names of taxa higher than genus-group and actually writes such names in capital letters.

Names of species

The name of a species is a combination of the name of a genus and a specific epithet (Art. 23.1). The specific epithet can be derived from any source whatever (Art. 23.2) and is either an adjective agreeing in gender with the generic name, a genitive noun, a nominative noun or a word treated as such, or two or more united or hyphenated words (see Table 6, pp. 52–53). The specific epithet may not exactly repeat the generic name, e.g. “Linaria linaria”; such a designation is a tautonym and, while permitted in zoological nomenclature, cannot be validly published under the Code (Art. 23.4).

Table 6.Download as CSV 

Examples of specific epithets. Thousands more examples can be found in Gledhill (2008).

Generic name	Specific epithet	Specific epithet: kind of word	Specific epithet: English meaning
Helianthus	annuus	adjective, masculine	annual
Quercus	alba	adjective, feminine	white
Rhododendron	arboreum	adjective, neuter	tree-like
Magnolia	grandiflora	compound of adjective+adjective, feminine	large-flowered
Thalictrum	aquilegiifolium	compound of noun+adjective, neuter	Aquilegia-leaved
Quercus	griffithii	genitive noun, masculine singular	Griffith’s
Ballota	deserti	genitive noun, masculine singular	of the desert
Strelitzia	reginae	genitive noun, feminine singular	the queen’s
Gladiolus	masoniorum	genitive noun, masculine plural	the Masons’
Coix	puellarum	genitive noun, feminine plural	the girls’
Glebionis	segetum	genitive noun, feminine plural	of the cornfields
Quercus	suber	nominative noun	cork tree
Nymphaea	lotus	nominative noun	lotus
Zea	mays	word treated as nominative noun	maize
Disa	longicornu	compound of adjective+nominative noun	long horn
Anthyllis	barba-jovis	hyphenated words, nominative noun- genitive noun	Jupiter’s beard
Aster	novae-angliae	hyphenated words, genitive adjective- genitive noun	of New England
Galanthus	reginae-olgae	hyphenated words, genitive noun- genitive noun	Queen Olga’s
Impatiens	noli-tangere	hyphenated words, verb-verb	do not touch

Note that specific epithets (and names in general) are not necessarily appropriate to the organism, and the Code does not require them to be appropriate, although when naming a new taxon you might want to choose an appropriate epithet. For example, Orobanche alba Stephan ex Willd. (“white”) is usually purplish red. Acer sempervirens L. (“evergreen”) is usually deciduous. Sedum anglicum Huds. (“English”) is widespread in western Europe and does not only occur in England. Sideritis cretica L. (“of or pertaining to Crete”) does not occur in Crete but in the Canary Islands.

The principle of priority is fundamental in determining the correct name for a taxon at the rank of family and below. Above the rank of family, priority does not apply. Priority means that if two or more names apply to the same taxon at the same rank, the earliest published, legitimate name (or its final epithet) must be used unless other rules prevent such use. Although several validly published names may apply to a taxon, there can be only one correct name for that taxon with a particular circumscription, position, and rank (Art. 11.1); the other names are synonyms.

Finding the correct name for a taxon can be a lengthy process involving specialist literature. Fortunately, a large body of older literature is now scanned and online, making it available to anyone with a computer and an internet connection. Checking such literature online is generally much faster than visiting a library and consulting the physical books.

Assume you have defined a taxon with a particular circumscription (what it includes), position (for nomenclatural purposes, to what genus or species it is assigned), and rank. This much is taxonomy, but it has nomenclatural consequences. You are faced with a list of names, or apparent names, that potentially apply to the taxon. From among these, how do you determine the correct name?

You can begin (see Fig. 9, p. 57) by disregarding any names or, rather, designations that are not effectively or not validly published. Then you can check the types of the validly published names and exclude any that do not refer to the taxon as circumscribed (typification is dealt with in detail in Chapter 7). Then you can relegate to synonymy any names that are illegitimate (Art. 6.4).

Figure 9.

The Nomenclatural Filter. Illustrating the steps to be taken in determining the correct name for a taxon. Based on a modification by David Hawksworth and John McNeill of a similar figure by Jeffrey (1989: 19).

It is very important to remember that names compete for priority only against names at the same rank (Art. 11.2), e.g. an earlier name of a variety cannot have priority over the later name of a species. For example, when Magnolia virginiana var. foetida L. 1753 is raised to specific rank, it is called M. grandiflora L. 1759, not M. foetida (L.) Sarg. 1889. Even though M. virginiana var. foetida is the earliest name, it cannot compete against names of species.

For taxa at the rank of family to genus, inclusive, the correct name is simply the earliest legitimate name at the same rank (Art. 11.3). For example, when Aesculus L. 1753, Pavia Mill. 1754, Calothyrsus Spach 1834, and Macrothyrsus Spach 1834 are referred to a single genus, its correct name is Aesculus, which is the earliest legitimate name at generic rank, and the other names are synonyms. Of course, the only validly published names applicable to your taxon could all be at other ranks, or they could all be illegitimate, or both. In that case you would need to publish the name of a new taxon, a name at new rank, or a replacement name.

Below the rank of genus, determining the correct name can be more complicated. It is not necessarily the earliest legitimate combination at the same rank and subordinate to the same genus or species, but rather the combination of the final epithet of the earliest legitimate name of the taxon at the same rank, with the correct name of the genus or species to which it is assigned (Art. 11.4; see Fig. 10, p. 58).

Figure 10.

Taxonomic treatment of Solanum chilense (Dunal) Reiche, from page 89 of a monograph in volume 84 of Systematic Botany Monographs by Peralta & al. (2008: 89). Reproduced by permission of the American Society of Plant Taxonomists. Components of this treatment are as follows:

• Accepted name: Solanum chilense; homotypic synonym: Lycopersicon chilense; citation of holotype at herbarium G-DC (Fig. 13, p. 66) and isotypes at B (destroyed), F (fragment), G, MPU (fragment), P, and WIR. The exclamation mark (!) placed after a herbarium code indicates that the cited specimen has been seen by the author(s). Herbarium codes follow Index Herbariorum (http://sweetgum.nybg.org/science/ih/).
• Heterotypic synonym: Lycopersicon atacamense; designation of lectotype at herbarium SGO.
• Heterotypic synonym: Lycopersicon bipinnatifidum; designation of lectotype at SGO (Fig. 14, p. 67) and citation of isolectotype at SGO.
• Heterotypic synonym: Lycopersicon puberulum; homotypic synonym: Lycopersicon peruvianum subsp. puberulum; designation of lectotype at SGO (Fig. 15, p. 68) and citation of isolectotype at WU.
• The homotypic synonyms (Lycopersicon chilense and Solanum chilense; L. puberulum and L. peruvianum subsp. puberulum) have the same types and therefore apply to the same taxa as a matter of fact. On the other hand, the heterotypic synonyms (Lycopersicon atacamense, L. bipinatifidum, L. chilense, and L. puberulum) have different types, and the authors of this monograph have made the taxonomic decision (a matter of opinion) that they all belong to the same species and to the genus Solanum. The earliest legitimate name for the taxon at specific rank is Lycopersicon chilense Dunal 1852; the combination of its final epithet, chilense, with Solanum, i.e. Solanum chilense, is therefore the correct name for the species.

Note that the earliest legitimate name of the taxon at the same rank may be in a different position to the one desired, i.e. the name of a subdivision of a genus or a species name combined under a different generic name, or the name of an infraspecific taxon combined under a different species name. In such a case, it is possible that the correct name has not yet been published, and it may be necessary to publish a new combination based on that earliest name.

If the combination resulting from this procedure would form a tautonym, which could not be validly published (e.g. “Cyanus cyanus”), or if it would be a later homonym, which would be illegitimate, the final epithet of the next earliest legitimate name at the same rank is to be used instead. If there is no final epithet available for use, a replacement name or the name of a new taxon may be published.

For example, Wei & Pedley (2010) recognized a taxon with a circumscription that included the types of the species names Millettia unijuga Gagnep. 1913 and Craspedolobium schochii Harms 1921; they considered the appropriate position to be subordinate to Craspedolobium and the appropriate rank to be species. The two names are legitimate and at the same rank and therefore compete for priority. Millettia unijuga is earlier, and so the correct name is the combination of its final epithet, unijuga, with Craspedolobium, i.e. C. unijugum (Gagnep.) Z. Wei & Pedley 2010, which had to be published as a new combination. Note also that, because unijuga is an adjective, its feminine ending, which agrees with the gender of Millettia, must be changed to unijugum to agree with the neuter gender of Craspedolobium (Art. 23.5).

Occasionally, simultaneously published names at the same rank will compete for priority. In such cases, the correct name is decided by a nomenclatural act, i.e. the first author to accept one name and relegate the others to synonymy in an effectively published work (Art. 11.5). For example, when Dentaria L. 1753 and Cardamine L. 1753 are united, the combined genus is called Cardamine because that name was accepted by Crantz (1769: 126–127, [142]), who first united the two, treating Dentaria as a synonym.

On the subject of simultaneously published names at the same rank, note that an autonym always has priority over the name(s) that established it (Art. 11.6). For example, Heracleum sibiricum includes two subspecies, named H. sibiricum subsp. lecokii and H. sibiricum subsp. sibiricum, the latter name automatically established upon valid publication of the former. When H. sibiricum, including both subspecies, is included in H. sphondylium as a single subspecies, the correct name of that subspecies is H. sphondylium subsp. sibiricum, not “H. sphondylium subsp. lecokii”. Note also that the basionym of H. sphondylium subsp. sibiricum is H. sibiricum, not H. sibiricum subsp. sibiricum.

There are exceptional circumstances under which a taxon can have more than one correct name in a particular circumscription, position, and rank. Eight automatically typified family names are permitted as alternatives to descriptive family names of long usage, e.g. Asteraceae is permitted as an alternative to Compositae (Art. 18.6; see Table 4, p. 50). There is also one subfamily name, Papilionoideae, permitted as an alternative to Faboideae when the Papilionaceae are included in the family Leguminosae as a subfamily (Art. 19.8).

Circumscription is an indication of the elements (e.g. subordinate taxa, synonyms, specimens, illustrations) that are included in a taxon. The names Tulipa saxatilis Sieber ex Spreng. 1825 and T. bakeri A.D. Hall 1938 can be applied to one broadly circumscribed species or to two narrowly circumscribed species; in the former case, T. saxatilis is accepted and T. bakeri is a synonym; in the latter case, both names are accepted. The name Taraxacum officinale W.W. Weber ex F.H. Wigg. can be applied to a very broadly circumscribed species that includes a huge range of segregate taxa, all the names of which (except T. officinale) are then synonyms. Alternatively, T. officinale and the numerous other names can be applied to very narrowly circumscribed segregate species, each of which then has an accepted name. When the same name is commonly used with such disparate circumscriptions, the terms sensu lato (in a broad/wide sense) and sensu stricto (in a strict/narrow sense) are often used, optionally abbreviated, e.g. T. officinale s.str. and T. officinale s.l.

Position means the placement of a taxon relative to other taxa in a classification, and for nomenclatural purposes this means its placement subordinate to a particular genus or species. The names Geranium zonale L. and Pelargonium zonale (L.) L’Hér. apply to the same species in different positions. If the name G. zonale is accepted, P. zonale is a synonym, and vice versa.

Rank means the position of the taxon in a hierarchy of consecutively subordinate ranks, e.g. genus, subgenus, section; or species, subspecies, variety (see Art. 3–4). The names Pinus brutia Ten. and P. halepensis subsp. brutia (Ten.) Holmboe apply to the same taxon at different ranks. If the name P. brutia is accepted, P. halepensis subsp. brutia is a synonym, and vice versa.

While legitimacy and illegitimacy were briefly discussed under basic concepts and terms (pp. 18–19), the present section examines in more detail the three ways in which a name can be illegitimate:

• When the name is a later homonym (Art. 53.1–53.3 and F.6.1)
• When the name was nomenclaturally superfluous when published (Art. 52.1)
• When the name is that of a family or subdivision of a family and it is based on an illegitimate generic name (Art. 18.3 and 19.6)

A name of a family, genus, or taxon below the rank of genus, unless conserved, protected, or sanctioned, is illegitimate if it is a later homonym (Fig. 11, p. 62). Homonyms are two or more names with exactly the same spelling (disregarding any rank-denoting term, e.g. sect., var.) but based on different types. They usually apply to different taxa, e.g. Vicia gigantea Hook. 1831, described from western North America, and Vicia gigantea Bunge 1833, a different species described from China. Bunge’s name was published two years later and is a later homonym and therefore illegitimate. It makes no difference if the earlier homonym is itself illegitimate, a name rejected under Art. 56.1 (see Chapter 8), or otherwise generally treated as a synonym, provided that it is validly published. If a supposed earlier homonym is not validly published, it has no status under the Code and the later name is not a homonym. So-called “parahomonyms”, names based on different types and spelled so similarly that they are likely to be confused, are to be treated as homonyms (Art. 53.2 and 53.3) and, in cases of doubt, a binding decision can be requested (Art. 53.4; see pp. 90–91). In rare cases, homonyms can be legitimate if they were published simultaneously and no earlier homonym exists (Art. 53 Note 1), but only one of them can be available for use (see Art. 53.5).

Figure 11.

A name that is illegitimate because it is a later homonym (Art. 53.1): Ranunculus muricatus Moench 1794 non L. 1753. Part of page 215 of Moench’s Methodus plantas horti botanici et agri Marburgensis (Moench, 1794: 215). This name is doubly illegitimate because it was also nomenclaturally superfluous when published (Art. 52.1). Components of the protologue are as follows:

• Specific epithet: “muricatus” (muricate), thus a later homonym of R. muricatus L. 1753 and therefore illegitimate under Art. 53.1.
• Diagnostic phrase name (polynomial): “[Ranunculus] muricatus, caule prostrato […] petalis minimis fugacibus.” (Ranunculus muricatus with prostrate stem […] petals very small, fleeting).
• Synonym: “Ranunculus parviflorus. Linn.” 1759. An earlier, validly published name at the same rank; citing it made R. muricatus Moench nomenclaturally superfluous when published, and therefore illegitimate under Art. 52.1, because Moench should have used R. parviflorus L. instead.
• Synonym: “Ranunculus hirsutus flore omnium minimo luteo.” A pre-starting-point phrase name referring to an illustration (Morison, 1680: sect. 4, t. 28, fig. 21).
• “Obs[ervatio]. Stamina vix decem.” (Observation. Stamens hardly ten).
• “h[abitat]. [in] H[orto]. Annua.” (It inhabits the garden [the botanic garden at Marburg, Germany]. Annual).

A name is illegitimate if it was nomenclaturally superfluous when it was published (Fig. 12, p. 63, see also Fig. 11, p. 62), unless it is conserved, protected, or sanctioned (see Chapter 8). Nomenclaturally superfluous when published means that the taxon to which it was applied, as circumscribed by its author, definitely included the type of a name that ought to have been adopted, or of which the epithet ought to have been adopted. The rules on priority (Art. 11.3 and 11.4) decide which name or epithet ought to have been adopted. Wintera Murray 1784 was nomenclaturally superfluous when published, and is therefore illegitimate, because Murray cited Drimys J.R. Forst. & G. Forst. 1775 as a synonym; Ranunculus lobatus Moench 1794 is illegitimate because Moench cited R. muricatus L. 1753 as a synonym (Fig. 12, p. 63). Both authors definitely included the type of the name that ought to have been adopted (by citing that name as a synonym; see Art. 52.2(e)).

Figure 12.

A name that is illegitimate because it was nomenclaturally superfluous when published (Art. 52.1): Ranunculus lobatus Moench. Part of page 214 of Moench’s Methodus plantas horti botanici et agri Marburgensis (Moench, 1794: 214). Components of the protologue are as follows:

• Specific epithet: “lobatus” (lobed).
• Diagnostic phrase name (polynomial): “[Ranunculus] lobatus, seminibus echinatis […] calycibus retroflexis petalis longioribus.” (Ranunculus lobatus with prickly seeds […] calyces bent backward, longer than petals).
• Synonym: “Ranunculus muricatus. Linn.” 1753. An earlier, validly published name at the same rank; citing it made R. lobatus nomenclaturally superfluous when published, and therefore illegitimate under Art. 52.1, because Moench should have used R. muricatus L. instead.
• Synonym: “Ranunculus echinatus stellatus creticus.” A pre-starting-point phrase name referring to an illustration (Morison, 1680: sect. 4, t. 29, fig. 24).
• “Obs[ervatio]. Stamina 14–20 nunquam plura.” (Observation. Stamens 14–20 never more).
• “h[abitat]. [in] H[orto]. Annua.” (It inhabits the garden [the botanic garden at Marburg, Germany]. Annual).

A name that was nomenclaturally superfluous when published is not illegitimate if it has a basionym (which is necessarily legitimate) or if it is formed from a legitimate generic name (Art. 52.4); it was still nomenclaturally superfluous (and therefore incorrect) when published, but it may become correct upon later use that excludes the element that caused the superfluity. Chloris radiata (L.) Sw. 1788 was nomenclaturally superfluous when published because Swartz cited the legitimate Andropogon fasciculatus L. 1753 as a synonym. However, it is not illegitimate since it has a basionym, Agrostis radiata L. 1759. Chloris radiata can be a correct name if Andropogon fasciculatus is treated as a different species. Carpinaceae Vest 1818 was nomenclaturally superfluous when published because Vest included Salix L., the type of Salicaceae Mirb. 1815, but it is not illegitimate because it is formed from Carpinus L., a legitimate generic name. If Salix is excluded, Carpinaceae can be a correct name.

Much rarer than the other two cases, a name of a family or subdivision of a family is illegitimate if it is based on an illegitimate generic name. For example, both Caryophyllaceae and Caryophylloideae are formed from the illegitimate name Caryophyllus Mill. 1754 non L. 1753, but because Caryophyllaceae has been conserved (see App. IIB), neither it nor Caryophylloideae is now illegitimate.

As mentioned under valid publication (Chapter 5), since 1 January 1958 when publishing the name of a new taxon at the rank of genus or below, it has been necessary to indicate the type, normally by designating it as such, otherwise the name is not validly published (Art. 40.1). Names that were published before 1958 without a type may be validly published, and a type can be subsequently designated for them. To indicate or designate the type of a name is to typify the name. A typified name has a type.

The holotype, lectotype, or neotype of a name of a species or infraspecific taxon is either a single specimen conserved in a single herbarium or it is an illustration (Art. 8.1), although for fossil-taxa it is always a specimen (Art. 8.5). The holotype of the name of a new taxon (non-fossil) published before 1 January 2007 can be a specimen or an illustration; when such a name is published on or after that date, the holotype must be a specimen (Art. 40.4), although an illustration is permitted as the holotype for names of microscopic algae and microfungi if preservation is difficult or impossible (Art. 40.5; see pp. 113 and 118). Note that this ban on illustrations as types applies only to holotypes of names of new taxa published on or after 1 January 2007. It does not apply to designating a lectotype, neotype, or epitype under Art. 9 for an already validly published name. Nor does it apply to a new combination, name at new rank, or replacement name.

A new combination, name at new rank, or replacement name is automatically typified by the type of its basionym or replaced synonym (Art. 7.3 and 7.4), e.g. Picea abies (L.) H. Karst. has the same type as its basionym, Pinus abies L.; Cedrus libani A. Rich. has the same type as its replaced synonym, Pinus cedrus L. The type of an autonym is that of the name from which it is derived (Art. 7.7), e.g. Poa L. subg. Poa has the same type as Poa L.; P. trivialis L. subsp. trivialis has the same type as P. trivialis L.

The type of the name of a genus or subdivision of a genus is in almost all cases the type of the name of a species (Art. 10.1), e.g. the type of Poa L. is the type of P. pratensis L.; the type of P. subg. Arctopoa (Griseb.) Probatova is the type of P. eminens C. Presl. For purposes of designation or citation of a type, it is sufficient to cite the species name alone, rather than its type specimen or illustration, e.g. the type of Poa can be cited simply as P. pratensis L., rather than the specimen Tzvelev N-257 (BM).

A name of a family or subdivision of a family is automatically typified by the type of the generic name from which it is formed (Art. 10.6). Thus the type of Poaceae is the type of Poa, i.e. the type of P. pratensis, i.e. the specimen Tzvelev N-257 (BM). The specially permitted descriptive family names of long usage are typified by the type of the corresponding alternative name, e.g. Gramineae has the same type as Poaceae. For purposes of designation or citation of a type, it is sufficient to cite the generic name alone.

This does not mean that the type of the name of a genus is a species or the type of the name of a family is a genus—that would be an oversimplification—so the terms “type species” and “type genus”, although sometimes used, are incorrect and should be avoided.

Note that the principle of typification does not apply above the rank of family, except that names formed from generic names (e.g. Magnoliophyta) are automatically typified by the same type as that of the generic name (Art. 10.10).

A specimen is defined as a gathering, or part of a gathering, of a single species or infraspecific taxon. Admixtures are disregarded, e.g. microscopic algae or fungi in environmental samples, inseparably mingled bryophytes, epiphytes or their substrate plants, parasites or their hosts. A gathering is defined as a collection presumed to be of a single taxon made by the same collector(s) at the same time from a single locality (and collecting numbers alone do not necessarily denote different gatherings). To be eligible as a type, a specimen must be preserved permanently and may not be a living organism or a culture, although fungi and algae may be preserved in a metabolically inactive state. A specimen can consist of a single organism, parts of one or several organisms, or of multiple small organisms. A specimen is usually mounted on a single herbarium sheet or in an equivalent preparation, such as a box, packet, jar, or microscope slide; it may be mounted on more than one sheet, slide, etc. so long as these parts are all clearly labelled as belonging to one specimen, or bear a single original label in common (e.g. the specimen folders in the Geneva herbaria), otherwise the parts are duplicate specimens belonging to the same gathering. It is also possible for two or more specimens belonging to different gatherings to be mounted, labelled accordingly, on a single herbarium sheet (e.g. numerous 19th century specimens in BM). The definitions of gathering, specimen, and duplicate are in Art. 8.2, 8.3, their footnotes, and 8.4.

The Code defines several different kinds of types, all belonging to names of species or infraspecific taxa. There is also the term original material, which can include some of these kinds of types. These terms are defined as follows:

• A holotype (Art. 9.1) is the one specimen (Fig. 13, p. 66) or illustration either indicated by the author as the nomenclatural type or used by the author when no type was indicated. As long as it exists, it fixes the application of the name concerned.
• An isotype (Art. 9.5) is any duplicate of the holotype and is always a specimen. If the holotype is an illustration there cannot be any isotypes.
• A syntype (Art. 9.6) is also always a specimen. It is any specimen cited in the protologue when there is no holotype, or any one of two or more specimens simultaneously designated in the protologue as types. Citation of a gathering, or part of a gathering, is considered to be citation of the included specimens, which are therefore syntypes.
• An isosyntype (Art. 9.4 footnote) is a duplicate of a syntype.
• A paratype (Art. 9.7) is any specimen cited in the protologue that is neither the holotype nor an isotype, nor one of the syntypes if in the protologue two or more specimens were simultaneously designated as types. Note that there is no such term “isoparatype” for a duplicate of a paratype.
• Original material (Art. 9.4) is defined by the Code as the holotype, isotypes, syntypes, isosyntypes, and paratypes of a name (either seen or not seen by the author), any illustrations published as part of the protologue, and any other specimens and published or unpublished illustrations that the author associated with the taxon and that were available to the author no later than the preparation of the validating description or diagnosis. Thus it is possible for uncited specimens and uncited illustrations to be part of the original material.
• A lectotype (Art. 9.3) is a specimen (Figs 14, 15, and 17, pp. 67, 68, and 76) or illustration (Fig. 18, p. 77) designated from the original material as the nomenclatural type if the name was published without a holotype, or if the holotype is lost or destroyed, or if a type is found to belong to more than one taxon.
• An isolectotype (Art. 9.4 footnote) is a duplicate of the lectotype.
• A neotype (Art. 9.8) is a specimen or illustration selected to serve as nomenclatural type if no original material is extant, or as long as it is missing.
• An isoneotype (Art. 9.4 footnote) is a duplicate of the neotype.
• An epitype (Art. 9.9) is a specimen or illustration selected to serve as an interpretative type when the holotype, lectotype, or previously designated neotype, or all original material associated with a validly published name, is demonstrably ambiguous and cannot be critically identified for purposes of the precise application of the name to a taxon. The epitype concept was new to the Code in the Tokyo Code (Greuter & al., 1994).
• An isoepitype (Art. 9.4 footnote) is a duplicate of the epitype.

Figure 14.

The lectotype of Lycopersicon bipinnatifidum Phil.: the specimen Rahmer s.n. in herbarium SGO (specimen accession no. 042822, barcode SGO000004414), showing longer leaves with more complex lobing than those of L. puberulum Phil. (Fig. 15, p. 68). Lycopersicon bipinnatifidum is a heterotypic synonym of both L. chilense Dunal (Fig. 13, p. 66) and L. puberulum. All three names have quite different-looking type specimens and they were originally applied to separate species. Despite these differences they are now considered to belong to the same variable species as a matter of taxonomic opinion. — Reproduced by permission of Museo Nacional de Historia Natural, Chile.

Figure 15.

The lectotype of Lycopersicon puberulum Phil.: the specimen Philippi s.n. in herbarium SGO (specimen accession no. 042824, barcode SGO000004416), showing shorter leaves with less complex lobing than those of L. bipinnatifidum Phil. (Fig. 14, p. 67). Lycopersicon puberulum is a heterotypic synonym of both L. chilense Dunal (Fig. 13, p. 66) and L. bipinnatifidum. All three names have quite different-looking type specimens and they were originally applied to separate species. Despite these differences they are now considered to belong to the same variable species as a matter of taxonomic opinion. — Reproduced by permission of Museo Nacional de Historia Natural, Chile.

Figure 16.

Typification flow chart.

Figure 17.

The lectotype of Zea mays L.: specimen no. 1096.1 in the Linnaean Herbarium (Herb. Linn.) at the Linnean Society of London (LINN). Note the annotations in Linnaeus’s handwriting to the right of the stem base: “1” is the species number in Species plantarum, and “Mays” is Linnaeus’s nomen triviale (i.e. specific epithet); they indicate that in preparing the protologue Linnaeus used this specimen, which is therefore original material. It was designated as the lectotype in a paper in volume 67 of the American Journal of Botany by Iltis & Doebley (1980: 1001). — Reproduced by permission of the Linnean Society of London (https://www.linnean.org/).

Figure 18.

Lectotype illustration of Phallus impudicus L.: tabula 83 in Micheli’s Nova plantarum genera (Micheli, 1729: t. 83). It was designated as the lectotype by Greuter & Kuyper in the book A list of Linnaean generic names and their types by Jarvis & al. (1993: 75). See Fig. 5 (p. 37) for the protologue of P. impudicus.

If one of the terms holotype, isotype, syntype, paratype, lectotype, neotype, or epitype is incorrectly used, i.e. in a sense that differs from its definition in the Code, that use is treated as an error to be corrected (Art. 9.10). For example, if a specimen is designated as a “lectotype” when it is not part of the original material, and in fact there is no extant original material, the incorrect use of the term “lectotype” is corrected to “neotype”. If a “paratype” is designated with a statement that it supports an ambiguous lectotype, the term “paratype” is corrected to “epitype”. A correction under Art. 9.10 does not have to be separately published, nor is the date of the original type designation affected, but that original designation must satisfy the rules for the relevant kind of type. For example, if a term used in a type designation published on or after 1 January 2001 is to be corrected to “lectotype”, “neotype”, or “epitype”, the designation must include the phrase “designated here” or an equivalent (Art. 7.11). If a term used in the protologue of the name of a new taxon is to be corrected to “holotype”, remember that such a name published on or after 1 January 1990 is not validly published if the type is not indicated using the word “typus” or “holotypus” or its abbreviation or its equivalent in a modern language (Art. 40.6). A name must be validly published in order to have any status under the Code and therefore to have a type; if it is not validly published, Art. 9.10 does not apply because there is nothing to correct.

Other terms you may encounter are “cotype”, an obsolete term meaning syntype (or sometimes isotype or paratype); “iconotype”, an unofficial term meaning either a holotype illustration or a “typotype”, the latter an unofficial term for a specimen that is the basis of a type illustration and that was not seen by the author of the name thus typified; “topotype”, an unofficial term meaning a specimen (which could be a neotype of epitype) collected from the original type locality; and “kleptotype”, an unofficial term meaning a type or a fragment of a type that should not be in its current location (because it was deliberately stolen, borrowed and not returned, etc.).

Paralectotype is an official term in the International Code of Zoological Nomenclature (Art. 73.2.2) for specimens that were syntypes prior to the designation of a lectotype; the paralectotypes cease to be syntypes, have no name-bearing function, and do not regain status as syntypes if the lectotype is lost or destroyed. The term is sometimes used unofficially in a similar sense in the nomenclature of algae, fungi, and plants, i.e. for the remaining syntypes after designation of a lectotype, but under the Code those syntypes either become isolectotypes (if they belong to the same gathering as the lectotype) or remain syntypes (if they belong to a different gathering). If the lectotype is lost or destroyed, any of the isolectotypes or remaining syntypes is eligible as the replacement lectotype.

In the protologue of the name of a new taxon at the rank of species or below published on or after 1 January 1958 there will generally be a single element, normally a specimen, explicitly designated as the type, i.e. the holotype. A name published before that date, however, may have more than one specimen designated as types (i.e. syntypes), or more than one specimen cited but none designated as a type (again, these are syntypes), or no specimens cited at all (Fig. 5, p. 37). In the last case, the name may lack any of the kinds of types defined above (pp. 70–71), but it may well have original material, which can include uncited specimens and cited and uncited illustrations. In all these cases where no holotype exists, the name may be typified by designating a lectotype or, where permitted, a neotype.

It was common practice for 18th-century authors to give a statement of provenance such as “Habitat in India orientali” (it dwells in eastern India), and less common to cite a collector or give further details pertaining to an actual specimen or gathering. A statement of provenance alone does not constitute citation of a specimen or gathering; concrete evidence is needed, such as a collector’s name, number, or date (see Art. 40 Note 1). For names with no cited specimens or gatherings, i.e. with no syntypes, it is very important to know where the author’s herbarium and types are now located (use Taxonomic literature, ed. 2 or “TL-2”; see pp. 151 and 154) and to look for original material that could provide a potential lectotype, i.e. uncited specimens that were or could have been in the author’s possession before the name was published and that bear annotations by the author linking the specimen to the name (Fig. 17, p. 76). I strongly recommend Order out of chaos (Jarvis, 2007) as the definitive guide to typifying Linnaean names. The methods described therein are often relevant to the typification of names published by other 18th- and early-19th-century authors.

In the 19th century, authors frequently cited collectors’ names in a protologue (Fig. 6, p. 38), often with collecting numbers, less often specifying a herbarium. These should be regarded as gatherings, comprising an undetermined number of specimens, unless there is evidence that individual specimens were being cited. Consulting the actual specimens, examining their annotations and features, often helps to determine which ones the author used and cited. Bear in mind that specimens may have been lost, destroyed, or moved to other herbaria since the author used them. They may even have been discarded or given away by the author (e.g. Linnaeus did this; see Jarvis, 2007: 170).

In the 20th century, citation of specimens became more and more detailed and precise, with specimens explicitly designated as types. Remember that the type concept, although dating back to the latter half of the 19th century, was not formally accepted internationally until the V International Botanical Congress, held in Cambridge in 1930. The 1958 starting date in Art. 40.1, requiring that a type be indicated for the name of a new taxon at the rank of genus or below, reflects that indicating types had become general practice by that time. The rules are even stricter for names published on or after 1 January 1990, when the type must be explicitly designated using the word “typus”, “holotypus”, or an equivalent in a modern language (or an abbreviation, e.g. “holo.”), and the single herbarium where the type is conserved must be specified.

Regardless of the date of publication of a name, if a single specimen in a specified herbarium is explicitly designated as the type, using that word or an equivalent, this is the holotype, i.e. “the one specimen … indicated by the author(s) as the nomenclatural type” (Art. 9.1). For names published before 1990, however, it is often uncertain if a holotype exists and, if it does, in which herbarium it is located. McNeill (2014) outlined the rules on holotype recognition and made suggestions for best practice.

If a name never had a holotype, or if the holotype has been lost or destroyed, or if the holotype is found to consist of more than one taxon, a lectotype may be designated (Art. 9.11). The same applies if a previously designated lectotype has been lost or destroyed or is found to consist of more than one taxon.

Lecto-, neo-, or epitypification is achieved by effective publication (Art. 7.10), and the first author who designates a lectotype, neotype, or epitype in accordance with the rules must be followed (Art. 9.19 and 9.20). The type must be definitely accepted as such by the author and it must be clearly indicated by direct citation including the word “type” or an equivalent (Art. 7.11).

The Code requires a strict procedure in lectotype designation (Art. 9.12). This can be best expressed by the flow chart in Fig. 16 (p. 74).

If a name has no extant original material, a neotype may be designated (Art. 9.13). If any original material exists, a neotype may not be designated, except under two special circumstances. The first is under Art. 9.16, i.e. to preserve the usage established by a holotype or lectotype that was lost or destroyed when all the remaining original material differs taxonomically from the destroyed type. The second is under Art. 9.19(c), i.e. to supersede a lectotype that is in serious conflict with the protologue when no other, non-conflicting original material exists.

When material designated as the type (holotype, lectotype, or neotype) is found to belong to more than one taxon, it is actually not a specimen, which is defined (Art. 8.2) as being “of a single species or infraspecific taxon”. In such a case, the name must remain attached to the part that complies with the definition of a specimen and corresponds most nearly with the original description or diagnosis (Art. 9.14). This is achieved (Art. 9.11) by designating the appropriate part as the lectotype or, if there is no original material, the neotype.

If the type or all elements eligible as the lectotype of a name are taxonomically ambiguous, then an epitype can be designated to help the interpretation of that type (Art. 9.9). For example, a holotype specimen might be nothing more than a wretched 200-year-old bare twig with degraded DNA; or the only possible lectotype could be a ridiculously oversimplified 17th-century woodcut illustration. When an epitype is designated, the supported holotype, lectotype, or neotype must also be explicitly cited (Art. 9.9).

Sometimes the only element—or all elements—available as the lectotype will be found to conflict with the current usage of a name. There is no taxonomic ambiguity, so an epitype cannot help. In such a case, you can maintain nomenclatural stability by bypassing lectotypification and proposing the name for conservation with a conserved type (see Chapter 8).

There are some additional requirements that come into effect on certain dates. When a lectotype, neotype, or epitype specimen is designated on or after 1 January 1990, the herbarium, collection, or institution in which the material is conserved must be specified (Art. 9.21 and 9.22). The same applies to an unpublished illustration (Art. 9.22). When designating an epitype that is a published illustration, a full and direct bibliographic reference (as defined in Art. 41.5) to that illustration must be provided (Art. 9.21). Furthermore, on or after 1 January 2001, the type designation must include the word “lectotypus”, “neotypus”, or “epitypus”, or its abbreviation (e.g. lecto., LT., neo., NT., epi.), or its equivalent in a modern language (e.g. lectotype, lectotipo) (Art. 9.23) and it must include the phrase “designated here” or an equivalent (Art. 7.11). See Figs 19 and 20 (pp. 78–79).

Figure 19.

Lectotypification of Merianthera burlemarxii Wurdack in a paper in volume 61 of the journal Taxon by Goldenberg & al. (2012: 1047). Lectotypifications and epitypifications of Ulva longissima Gunnerus and U. maxima Gunnerus in another paper in the same volume by Jørgensen (2012: 1094). Reproduced by permission of the International Association for Plant Taxonomy. Components of the typifications are as follows:

• Use of the words “lectotype” and “epitype”, as required by Art. 9.23.
• Use of the phrase “designated here”, as required by Art. 7.11.
• Specification of the herbaria in which the lectotype and epitype specimens are conserved (US, TRH), as required by Art. 9.22 and 9.21, respectively.

Figure 20.

Lectotypification and epitypification of Boletus fechtneri Velen. in a paper in volume 71 of the journal Czech Mycology by Janda & al. (2019: 16). The protologue of Boletus fechtneri (Velenovský, 1922: 704–705) cited no specimens, but there is uncited original material (Art. 9.4(a)), i.e. a specimen collected by František Fechtner in 1921 and determined by Velenovský, which is the only available choice of lectotype. Reproduced by permission of the Czech Scientific Society for Mycology. Components of the typifications are as follows:

• Use of the words “lectotype” and “epitype”, as required by Art. 9.23.
• Use of the phrase “designated here”, as required by Art. 7.11.
• Specification of the herbaria in which the lectotype and epitype specimens are conserved (PRC, PRM), as required by Art. 9.22 and 9.21, respectively.
• Citation of the identifiers issued for the lecto- and epitypification by the recognized repository, MycoBank (“MBT 381727”, “MBT 381728”), as required by Art. F.5.4 in type designations for fungal names from 2019 onward.
• Citation of an isoepitype in the herbarium BRNM.
• Herbarium codes PRC, PRM, and BRNM are followed by numbers identifying the specimens (see Rec. 9C.1).
• Statement (Janda & al., 2019: 20) explaining in what way the lectotype is ambiguous such that epitypification is necessary (Rec. 9B.2): lacks the colour typical of the species; lacks mature spores; formaldehyde in the preserving liquid prevents DNA extraction.
• Selection of the epitype specimen to have similar locality, habitat, and morphological details to those mentioned in the protologue.
• Because Butyriboletus fechtneri (Velen.) D. Arora & J.L. Frank and its basionym Boletus fechtneri have the same type (Art. 7.3), both names are lecto- and epitypified here.
• Boletus appendiculatus subsp. pallescens Konrad is a heterotypic synonym and is not therefore typified here.

Note that many pre-2001 lecto- and neotypifications, often unintended, exist in the literature. An author merely had to write a phrase like “Type: Smith 123 (K)” and, if a specimen Smith 123 existed in the Kew herbarium and was eligible as the lectotype or neotype, the name was so typified. Today it would be necessary to write “Lectotype designated here: Smith 123 (K).”

The rules for designating a lectotype or neotype extend also to names of genera and subdivisions of genera and are found in Art. 10. The terms “holotype”, “syntype”, “lectotype”, and “neotype” are often used in this context, by analogy with the typification of names of species and infraspecific taxa, although strictly speaking these terms are not applicable to types of names above the rank of species. For example, if the name of a new genus is published with two or more species names included (“syntypes”), and no “holotype” of the generic name is indicated in the protologue (it would need to be a pre-1958 name in order to be validly published; see Art. 40.1), one of those species names may subsequently be designated as the “lectotype” of the generic name under Art. 10.2. If the name of a new genus is published with no species names included, or, more precisely, with no type of any validly published species name definitely included (see Art. 10.3), a type must otherwise be chosen, i.e. a species name may subsequently be designated as the “neotype”, again under Art. 10.2. It is actually the type of the species name that is the type of the generic name, but, as mentioned earlier, for purposes of designation or citation of the type, the species name alone suffices (Art. 10.1).

The only circumstance in which the type of a generic name may be a specimen or illustration that is not the type of a validly published species name is when the generic name is conserved with a conserved type (Art. 10.4; see Art. 14.9). For example, the conserved type of Pseudolarix Gordon (see App. III) is “[specimen] cult. in Anglia, ex Herb. George Gordon (K barcode K000287582)”, which is a specimen referable to P. amabilis (J. Nelson) Rehder but is not the type of that species name.

In certain cases, typification of the name of a subdivision of a genus is automatic, i.e. when the epithet is the same as, or derived from, the epithet one of the species names included in the protologue (Art. 10.8). For example, the type of Euphorbia subg. Esula Pers. is E. esula L. However, designation of a different type by the original author overrides this automatic typification.

As with lecto- and neotypifications of names of species and infraspecific taxa, the first author who designates a type for a name of a genus or subdivision of a genus in accordance with the rules must be followed (Art. 10.5). However, if a “neotype” is not conspecific with any of the material associated with the protologue, it is to be superseded (Art. 10.2 last sentence), presumably by a type conspecific with at least some material associated with the protologue.

A choice of type of a name of a genus or subdivision of a genus may also be superseded if it was based on a largely mechanical method of selection (Art. 10.5). It is superseded by any later, different choice that did not use such a method, unless, in the interval, the original choice was affirmed, i.e. adopted in a publication that did not use such a method. The phrase “a largely mechanical method of selection” was not properly defined in previous editions of the Code, but now the Shenzhen Code includes detailed criteria (Art. 10.6 and 10.7) enabling you to determine whether a publication used such a method of selecting types. These are publications that followed the so-called “Philadelphia Code” (Arthur & al., 1904) or the American Code of Botanical Nomenclature (Arthur & al., 1907).

Conservation is dealt with under Art. 14 of the Code. Under Art. 14.1, a conserved name is legitimate even though it may have been illegitimate when published. It is possible to conserve names at the ranks of family, genus, and species; in addition, a name of a subdivision of a genus or infraspecific taxon can be conserved when it is the basionym of a generic or species name that could not continue to be used in its current sense without conservation. Conserved names are listed in the Appendices of the Code: App. IIA and IIB for names of families, App. III for names of genera and subdivisions of genera, and App. IV for names of species and infraspecific taxa. A conserved name may be indicated as such with the abbreviation “nom. cons.” (Rec. 50E.1), which stands for nomen conservandum, Latin for “name to be conserved”, e.g. Malvaceae Juss., nom. cons., Bambusa Schreb., nom. cons., Galactites tomentosus Moench, nom. cons.

A conserved name at any rank is conserved against all earlier homonyms (Art. 14.10), whether or not those conserved-against, i.e. rejected, homonyms are listed alongside the conserved name in the relevant Appendix. For example, Ipomoea discolor (Kunth) G. Don 1837–1838 is conserved against I. discolor Jacq. 1798, and the latter name is listed alongside the former in App. IV; Blumea DC. 1833 is conserved against Blumea Rchb. 1828–1829 even though the latter name is not listed alongside the former in App. III. Conservation does not make the earlier homonym illegitimate; although unavailable for use, it may serve as a basionym.

A conserved name of a family or genus is conserved against all other names at the same rank based on the same type (homotypic synonyms), whether or not the rejected names are listed alongside the conserved name in the relevant Appendix (Art. 14.4). The conserved name is also conserved against those names based on different types (heterotypic synonyms) that are listed as rejected in the entry in App. IIA or III. For example, Corydalis DC. 1805 is listed in App. III as conserved against the earlier homonym Corydalis Medik. 1789, the earlier homotypic synonym Pistolochia Bernh. 1800, and three earlier heterotypic synonyms: Capnoides Mill. 1754, Cysticapnos Mill. 1754, and Pseudo-fumaria Medik. 1789. These five conserved-against names are all rejected in favour of Corydalis DC. However, the three heterotypic synonyms are not rejected under all circumstances; any or all of them may be adopted as correct names if they are considered to apply to genera distinct from Corydalis DC. (Art. 14.6).

A conserved name of a species is conserved against all names listed as rejected in the entry in App. IV, and against all combinations based on the rejected names (Art. 14.4). For example, Cactus cruciformis Vell. 1829 is conserved against the earlier homotypic synonym Cereus squamulosus Salm-Dyck ex DC. 1828 and the three earlier heterotypic synonyms Cereus tenuispinus Haw. 1827, C. myosurus Salm-Dyck ex DC. 1828, and C. tenuis DC. 1828. These four conserved-against names are all rejected in favour of Cactus cruciformis. The same applies to all combinations that are based on them. However, under Art. 14.6, any or all of the three heterotypic synonyms may be adopted as correct names if they are considered to apply to species distinct from C. cruciformis.

When a species name is conserved against a name that is based on an earlier name, that earlier name may still be used because it is not listed as rejected and it is not a combination based on a rejected name. For example, Lycopersicon esculentum Mill. 1768 is conserved against L. lycopersicum (L.) H. Karst. 1882, which is based on Solanum lycopersicum L. 1753. This conservation does not prevent the use of S. lycopersicum or indeed any name based on it except L. lycopersicum.

A name may be conserved with a particular type (Art. 14.9) or to preserve a particular spelling or gender (Art. 14.11). When a type is conserved, it may be different from that determined by the Code or designated by the original author. This is a very useful tool for maintaining nomenclatural stability when an existing type, or an automatic type (e.g. under Art. 7.5 for a name illegitimate under Art. 52.1), or the only element(s) available for designation as the type, conflict with the current usage of the name. You also have the advantage of being able to choose a high-quality, recent specimen with duplicates widely distributed in several herbaria. There is no obligation to “pay homage” by choosing an element connected with the original author(s), although it may be useful to choose a specimen collected near the original type locality.

When a conserved name competes with one or more heterotypic synonyms against which it is not explicitly conserved (i.e. the synonyms are not listed as rejected in the entry in the Appendix), under Art. 14.5 the earliest of the competing names is adopted in accordance with the rules on priority (Art. 11). For example, Mahonia Nutt. 1818 is listed in App. III as conserved, but not explicitly so against any name. If it is united with Berberis L. 1753, the combined genus bears the name Berberis, which has priority.

There is an exception in Art. 14.5: the conserved family names listed in App. IIB are conserved against all unlisted names. For example, Combretaceae R. Br. 1810 is listed in App. IIB and is therefore conserved against the unlisted earlier heterotypic name Terminaliaceae J. St.-Hil. 1805. For a family circumscribed to include Terminalia L. as well as Combretum Loefl., Terminaliaceae would have priority over Combretaceae if the latter were not conserved.

The family names listed in App. IIB are further protected by Art. 14.14, which rules that the places of publication cited are treated as correct in all circumstances and consequently are not to be changed, even when otherwise such a name would not be validly published or when it is a later isonym. If someone digs in the literature and finds an earlier place of valid publication for one of the names in App. IIB, the current entry in the Appendix is protected even though it is a later isonym, which would otherwise have no status under the Code (Art. 6 Note 2).

A rejected name (or a combination based on one) may not be adopted for a taxon that includes the type of the corresponding conserved name (Art. 14.7). To illustrate this, consider Enallagma (Miers) Baill. 1888, conserved against Dendrosicus Raf. 1838, but not against Amphitecna Miers 1868. If all three names are applied to the same genus (so that the genus includes all three types), under Art. 14.5 you might expect the genus to be called Dendrosicus, because that is the earliest name, but in fact it is the second earliest name, Amphitecna, because Dendrosicus cannot be restored for a genus that includes the type of Enallagma. No such restriction applies to Amphitecna, because Enallagma is not conserved against it.

Entries on the lists of conserved names may not be deleted (Art. 14.13), but they may be added to or amended (Art. 14.12); amendment includes changing the listed type or spelling of an already conserved name (Art. 14.8).

Protection, which allows submission of lists of names to be treated as conserved, was a new concept introduced at the Melbourne Congress of 2011, but there were no actual protected names until the Shenzhen Congress of 2017, when the scope of protection was also expanded. Protection applies only to names of organisms treated as fungi and is dealt with in Chapter F, under Art. F.2. The concept is essentially the same as conservation, except that the names are submitted in lists and each protected name is treated as conserved against any competing listed or unlisted synonyms or homonyms (including sanctioned names; see Chapter 11). In this respect, protected names behave like the conserved names of families of bryophytes and spermatophytes in App. IIB. The lists are submitted to the General Committee but by publication in IMA Fungus, the journal of the International Mycological Association. The General Committee refers the lists to the Nomenclature Committee for Fungi for examination by subcommittees established by that Committee in consultation with the General Committee and appropriate international bodies. The voting and approval procedure is the same as for conservation proposals. The protected names appear in the relevant Appendices of conserved names (App. IIA, III, or IV), indicated by “(P)” and, if Congress approval is still pending, preceded by an asterisk (*) . The lists of protected names can be revised by the same process, and conservation under Art. 14 overrides protection under Art. F.2.

The Code also contains provisions for the formal rejection of any name—at any rank—that would cause a disadvantageous nomenclatural change (Art. 56.1). No name needs to be conserved against such a rejected name. It is rejected in all circumstances and cannot be used; all combinations based on it are likewise rejected. Such names are called nomina utique rejicienda (names to be rejected in any case, suppressed names) and are listed in App. V. A nomen utique rejiciendum may be indicated as such with the abbreviation “nom. utique rej.” or (following Rec. 50E.2) “nom. rej.”, e.g. Cacalia L., nom. rej., Peziza [unranked] Phialea Pers., nom. rej., Rosa eglanteria L., nom. rej., Actaea spicata var. alba L., nom. rej.

Although such a rejected name becomes unavailable for use, a later homonym of it remains illegitimate (Art. 53 Note 2), so if you want to make a later homonym legitimate, you must conserve it against the earlier homonym.

The procedure for proposing a name for rejection (Art. 56.2), and its journey through the committees to a Congress, is the same as that for conservation. The same guidelines apply (McNeill & al., 2018). The proposal submitted to Taxon should quantify how widespread and traditional is the usage of the name compared with the name(s) that it threatens. Rejection, if recommended, takes effect non-retroactively on publication of the General Committee’s report (Art. 56.3), but is subject to the decision of a later International Botanical Congress. The name appears in App. V, preceded by an asterisk (*) , which is deleted after approval by a Congress.

For names of organisms treated as fungi, it is also possible to submit lists of names for rejection under Art. F.7. The procedure parallels that for protection under Art. F.2, and the lists are submitted to the General Committee by publication in IMA Fungus. The rejected names are to be treated as rejected under Art. 56.1, except that they may become eligible for use by conservation under Art. 14. They would presumably be listed in App. V, although to date no lists of names have been submitted for rejection.

Note that even if a proposal to conserve or reject a name is not submitted, the Code provides, under Art. 57.1, protection for a name that has been widely and persistently used for a taxon or taxa not including its type. Such a name is not to be used in a sense that conflicts with current usage unless and until a proposal to deal with it under Art. 14.1 or 56.1 has been submitted and rejected. In other words, if a name has had and still has a widespread, traditional usage for a particular taxon, but its type in fact belongs to a different taxon, the usage of the name must not be changed from the traditional sense to the sense of its type, which would be the correct action if Art. 57.1 did not exist. Such a change in usage can only occur if a proposal to conserve or reject the name is submitted and is subsequently rejected, i.e. the General Committee recommends not to conserve or not to reject the name.

On rare occasions, a particular publication is found to contain so many disruptive names that it is much simpler to propose the whole publication for suppression under Art. 34.1 than to propose each disruptive name individually for rejection under Art. 56.1. Such publications are called suppressed works, or opera utique oppressa (works suppressed in any case), and are listed in App. I. Names of taxa in specified ranks in a suppressed work are not validly published, e.g. names of species in Gandoger (1883–1891) and names at all ranks in Haller (1753). Suppression also makes any nomenclatural acts in the work ineffective (e.g. lectotypifications; see Art. 34.1 footnote) if they are associated with names at the specified ranks. Suppression is retroactive, so it is as if the works had always been suppressed. Most of the suppressed works listed in App. I are from the 18th century, although one is relatively recent, from the 1990s (Motyka, 1995–1996). The procedure for proposing a work for suppression and the mechanism by which it becomes suppressed and enters App. I are essentially the same as those for conservation and rejection, although more than one specialist committee may consider the proposal if the work covers, e.g., both plants and algae. If suppression is recommended, it takes effect retroactively on publication of the General Committee’s report (Art. 34.2), but is subject to the decision of a later International Botanical Congress. The work appears in App. I, preceded by an asterisk (*) , which is deleted after approval by a Congress.

A binding decision provides a ruling in a situation of doubt. It is made by an International Botanical Congress, based on a recommendation by the General Committee, in turn based on a recommendation by one of the specialist committees, resulting from a request from an individual. There are currently two kinds of binding decisions: those on the adequacy of descriptive statements for the purpose of valid publication and those on treating confusingly similar names as homonyms.

The arrangement and contents of the seven Appendices that deal with conserved and rejected names, suppressed works, and binding decisions are given below. Note that, except for the introductions to each Appendix, the texts are in Latin. This may not be immediately obvious, because most of the text consists of scientific names, abbreviated authors’ names, and bibliographic references, but you will notice Latin words such as ad, icon, and non designatus, and various abbreviations, such as nom. cons., typ. cons., and prim. These and the symbols *, (=) , (≡) , (H), (NH), and (P) are listed in Table 7 (p. 93–94) together with their meanings (they are also included in the list of abbreviations, acronyms, symbols, and Latin words on pp. 166–173).

Table 7.Download as CSV 

Symbols, Latin words, and abbreviations of Latin words used in Appendices I–VII of the Code.

Term	Meaning
*	when preceding an entry indicates a proposal approved by the General Committee; retention or rejection of the name or suppression of the publication is authorized subject to the decision of a later International Botanical Congress
(=)	heterotypic (i.e. taxonomic) synonym
(≡)	homotypic (i.e. nomenclatural) synonym
(H)	homonym
(NH)	not a homonym
(P)	protected name, only for names of fungi
ad t.	ad tabulam, at the plate, used when citing a place of publication associated with an illustration
ante	before, used when citing a date
cancellans	cancelling, used for a corrected page inserted in a book, replacing the cancelled page
deest	it is missing, used for a missing type specimen
etiam vide	see also
ex	from, used in author citations or to indicate the source of a type specimen
gen. fem. cons.	genus femininum conservandum, feminine gender to be conserved
gen. masc. cons.	genus masculinum conservandum, masculine gender to be conserved
gen. neut. cons.	genus neutrum conservandum, neuter gender to be conserved
icon	image, i.e. an illustration
ined.	ineditus, not published
med.	medio, mid, in the middle (in a month or year), used when citing a date
nom. alt.	nomen alternativum, alternative name
nom. cons.	nomen conservandum, name to be conserved
nom. illeg.	nomen illegitimum, illegitimate name
nom. rej.	nomen rejiciendum, name to be rejected
nom. utique rej.	nomen utique rejiciendum, name to be rejected outright, a suppressed name
non designatus	not designated
orth. cons.	orthographia conservanda, orthography (i.e. spelling) to be conserved
post	after, used when citing a date
prim.	primo, at the beginning, early (in a month or year), used when citing a date
q.v.	quod vide, which see
s.ann.	sine anno, without year
s.coll.	sine collectore, without collector
s.loc.	sine loco, without locality
sero	late (in a month or year), used when citing a date
sub	under
typ. cons.	typus conservandus, type to be conserved
typ. des.	typi designatio, designation of type
typus	type
vide	see (imperative)

In most cases, the correct author citation for a name is simply the author(s) cited immediately following the name, or if no author(s) are cited thus, the author(s) of the publication that contains the protologue of the name (see Art. 46 Note 1). That publication might be a book, a chapter of a book, a treatment of a family or genus in a Flora, or a paper in a journal. When the publication is part of a larger work, the relevant authorship is that of the part, not of the larger work (Art. 46.6).

In older works, the author citation is often lacking, e.g. in Linnaeus’s Species plantarum (Linnaeus, 1753) you will not find “L.”, “Linn.”, “Linné ”, or “Linnaeus” cited after the names, yet Linnaeus is the sole author of the book and is therefore the author of the names therein.

In most modern protologues, a new name is immediately followed by its author citation. For example, “Agrostopoa Davidse, Soreng & P.M. Peterson, gen. nov.” appears in a paper by Davidse, Soreng, and Peterson (Davidse & al., 2009); “Tainus Torr.-Montúfar, H. Ochot. & Borsch, gen. nov.” appears in a paper by Torres-Montúfar, Borsch, Fuentes, Clase, Peguero, and Ochoterena (Torres-Montúfar & al., 2017). In these examples, the author citations either exactly match the authorship of the publication or have authors in common. These are uncomplicated cases where you can simply accept the author citation provided.

A name, in its protologue, may appear with an author citation that has no person in common with the authorship of the publication that contains the protologue. In most such cases, the correct author citation is not what appears in the publication but may consist of both sets of authors separated by the word “ex”, in the format “[author(s) as cited] ex [author(s) of the publication]” (Art. 46.5). Note that citing “[author(s) as cited] ex” is optional, and it is equally correct simply to cite the authors of the publication. For example, Seemann was the sole author of a publication (Seemann, 1865–1873) in which he published the name of a new species, ascribing it to Nuttall, thus: “G[ossypium]. tomentosum, Nutt. mss.” The correct citation is either Gossypium tomentosum Nutt. ex Seem. or Gossypium tomentosum Seem., but not “Gossypium tomentosum Nutt.” When “ex” is used, it separates what might be called an “honorary” author (Nuttall) from the actual author who validly published the name (Seemann).

Authors of publications often cite such honorary authors when they feel some credit for the new name is due, e.g. the name was first used in an annotation of a herbarium specimen or in correspondence (i.e. it was not effectively published), or it was effectively but not validly published previously.

You will often see these “ex” citations actually used in protologues. If you are publishing a new name and wish to ascribe it to someone else, you yourself can use an “ex” citation, i.e. “[his/her name] ex [your name]” (Art. 46.10).

A useful rule to remember is that the same author cannot correctly appear on both sides of an “ex” citation. When a cited authorship and the authorship of the publication have at least one person in common, the cited authorship is always accepted as correct (Art. 46.2 last sentence). For example, the authorship of Tainus, mentioned above (p. 96), cannot be “Torr.-Montúfar, H. Ochot. & Borsch ex Torr.-Montúfar & al.”

When a name is cited with its author and a full bibliographic citation, sometimes the authorship of the publication as a whole may differ from the correct author citation of the name. In that case, both may be cited, separated by the word “in” (Art. 46 Note 2). For example, Carex continua C.B. Clarke in Hooker, Fl. Brit. India 6: 717. 1894, where Clarke is the author of both the name, which appears as “C. continua, C. B. Clarke”, and the treatment of the Cyperaceae in The Flora of British India, indicated by “CYPERACEÆ. (C. B. Clarke)” at the top of the page, whereas Hooker is the general author of the Flora (Hooker, 1872–1897), indicated by “by Sir J. D. Hooker” on the title pages of the volumes.

Note that the authorship following “in” is part of a bibliographic citation and is not part of the authorship of the name; it is therefore omitted unless a full bibliographic citation follows, and then it is preferably not abbreviated. For example, you would not write “Carex continua C.B. Clarke in Hooker” by itself nor “Carex continua C.B. Clarke in Hook., Fl. Brit. India 6: 717. 1894”.

When a journal is involved, the authors of the publication, i.e. the whole paper, are usually omitted, e.g. Cleretum clavatum (Haw.) Klak in Taxon 61: 304. 2012, not “Cleretum clavatum (Haw.) Klak in Klak & Bruyns, Taxon 61: 304. 2012”, where Klak is the sole author of the name in a paper jointly authored by Klak and Bruyns in the journal Taxon (Klak & Bruyns, 2012).

For a new combination or name at new rank, the author of the basionym is cited in parentheses immediately before the author of the new name (Art. 49.1). For example, Smith is the author of the name at new rank, Drynaria (Bory) J. Sm., and Bory is the author of its basionym, Polypodium subg. Drynaria Bory. Or in the example above (p. 97), Klak is the author of the new combination, Cleretum clavatum (Haw.) Klak, and Haworth is the author of its basionym, Mesembryanthemum clavatum Haw. Such parenthetical authors are cited only when a name has a basionym, hence the alternative term, basionym author.

It follows, then, that for a replacement name the author of the replaced synonym is not cited in parentheses. For example, Ziziphus jujuba Mill., which is a replacement name for Rhamnus zizyphus L., is not cited as Z. jujuba “(L.) Mill.” The same applies to a replacement name that re-uses the final epithet of its replaced synonym (explicitly permitted under Art. 58.1), e.g. Calandrinia polyandra Benth. is a replacement name for Talinum polyandrum Hook. 1855, which is an illegitimate later homonym of T. polyandrum Ruiz & Pav. 1798; the author citation of C. polyandra is Benth., not “(Hook.) Benth.”

Moreover, parenthetical authors are not cited for suprageneric names (Art. 49.2). For example, even though Illiciaceae A.C. Sm. 1947 was validly published by reference to Illicieae DC. 1824, and is a name at new rank, it is not cited as Illiciaceae “(DC.) A.C. Sm.”

• Alphabet and form. Strictly speaking this is not orthography and it does affect valid publication: a name must be composed only of letters of the Latin alphabet and have a form that complies with the provisions of Art. 16–27 (Art. 32.1). These provisions are the rules on the formation of names discussed on pp. 48–54.
• Letters and ligatures foreign to classical Latin (Art. 60.4). The letters k, w, and y are permissible in scientific names, but other letters and ligatures are to be transcribed (e.g. German ß to ss).
• Letters u / v or i / j used interchangeably or in any other way incompatible with modern typographical or nomenclatural practices (Art. 60.5 and 60.6). Such letters are to be transcribed in conformity with modern nomenclatural usage, e.g. “Vredo pvstvlata” is to be spelled Uredo pustulata. When the diphthong ey (ευ) derived from Greek words is transcribed as ev, this is treated as an error correctable to eu, e.g. “Evonymus” is to be spelled Euonymus. When names or epithets of Latin but not Greek origin include the letter i as a semi-vowel (followed by another vowel), this is treated as an error correctable to j, e.g. Brachypodium “iaponicum” is to be spelled Brachypodium japonicum.
• Diacritical signs and ligatures (Art. 60.7). Diacritical signs are not used in scientific names and are to be transcribed (e.g. ä → ae; ö → oe; ü → ue; é, è, ê → e; ñ → n; ø → oe; å → ao). Note that the diaeresis (e.g. Cephaëlis, Isoëtes) is a phonetic device not considered to alter the spelling; as such, its use is optional. The ligatures æ and œ are to be replaced by the separate letters ae and oe.
• Terminations (endings) (Art. 32.2). If a name has Latin or transcribed Greek termination that is against the rules, it is to be corrected without change of the author citation or date of the name (Art. 32.2). This includes suprageneric names with improper terminations (Art. 16.3, 18.4, and 19.7) and, among other errors, an adjectival epithet that does not agree in gender with the generic name (Art. 21.2, 23.5, and 24.2). For example, Aster “nigromontana” is correctable to A. nigromontanus because the generic name Aster is masculine. Also a correctable error is usage of the word element -cola as an adjective (Art. 23.5), e.g. Erigeron “alpicolus” is correctable to E. alpicola.
• Terminations of epithets honouring people (Art. 60.8 and Rec. 60C.1). The use of a termination (for example -i, -ii, -ae, -iae, -anus, or -ianus) contrary to Art. 60.8 is to be corrected to conform with it. However, terminations of epithets formed in accordance with Rec. 60C.1 are not to be corrected. For example, the epithet of Quercus michauxii was formed in accordance with Art. 60.8 and is not therefore to be changed. However, the epithet of Rhododendron “potanini” is contrary to Art. 60.8 and was not formed in accordance with Rec. 60C.1; it is therefore to be corrected to potaninii. On the other hand, the epithet of Phoenix theophrasti was formed in accordance with Rec. 60C.1 and is not therefore to be changed to “theophrastii” or anything else. See More on terminations of epithets honouring people, pp. 103–108.
• Intentional latinizations (Art. 60.9). The essence of this rule, and there are some exceptions, is that intentional latinizations of personal, geographical, or vernacular names are to be preserved. For example, Abies alcoquiana commemorates “Rutherford Alcock Esq.”, implying an intentional latinization of Alcock to Alcoquius. The spelling must not be changed to “alcockiana”.
• Compound epithets (Art. 60.10 and Rec. 60G.1). An adjectival epithet combining elements derived from two or more Greek or Latin words that is not formed in accordance with Art. 60.10 is to be corrected to conform with it (with some exceptions). For example, the epithet “cannaefolia” must be changed to cannifolia. See More on compound epithets, pp. 108–109.
• Hyphens (Art. 60.11 and 60.12). In a compound epithet, a hyphen is treated as an error to be corrected by deletion of the hyphen, e.g. Acer “pseudo-platanus” and Scirpus sect. “Pseudo-eriophorum” are to be spelled Acer pseudoplatanus and Scirpus sect. Pseudoeriophorum. A hyphen is permitted only when the epithet is formed of words that usually stand independently, e.g. Vitis novae-angliae (of New England), or when the letters before and after the hyphen are the same, e.g.Athyrium austro-occidentale. Note that if an epithet consists of two or more words, Art. 23.1 rules that they are to be united or hyphenated in accordance with Art. 60.11, e.g. Coix “lacryma jobi”, originally published with a space but no hyphen, in which the two words usually stand independently (Job’s tears), is to be spelled Coix lacryma-jobi. When a generic name is published with a hyphen, the hyphen is to be retained (Art. 60 Note 6), unless it is the name of a fossil-genus, when the hyphen is always to be deleted (Art. 60.12).
• Apostrophes, quotation marks, and full stops (periods) (Art. 60.13). When an apostrophe or quotation mark is used in an epithet, it is to be deleted, e.g. Lycium “o’donellii” is to be spelled Lycium odonellii. However, if it follows the letter m to represent the patronymic prefix Mc or M^c, it is replaced by the letter c, e.g. “Stobaea M‘Kenii” is to be spelled Stobaea mckenii. When a full stop is used in an epithet that is derived from a personal or geographical name that contains this full stop, the epithet is to be expanded (see Abbreviations, below) or, if nomenclatural tradition does not support expansion, the full stop is to be deleted, e.g. Nesoluma “St.-Johnianum” is to be spelled Nesoluma st-johnianum.
• Abbreviations (Art. 60.14). Abbreviated names and epithets are to be expanded in conformity with nomenclatural tradition, e.g. Allium “a.-bolosii” is to be spelled Allium antonii-bolosii.
• Epithets of fungal names (Art. F.9.1). When derived from the generic name of an associated organism, epithets are to be spelled in accordance with the accepted spelling of the name of that organism. For example, Phyllachora “anonicola” is to be corrected to Phyllachora annonicola because the accepted spelling of the name of the associated organism is Annona, not “Anona”.

Article 60.8, concerning terminations of epithets that honour people, can be explained as follows: When a specific or infraspecific epithet that is derived from a personal name is formed in accordance with Art. 60.8, it cannot be changed. When it is contrary to Art. 60.8, it must be corrected so that it accords, unless it was formed in accordance with Rec. 60C.1, in which case, again, it cannot be changed.

Article 60.8 concerns the formation of specific and infraspecific epithets that are derived from unlatinized personal names. For example, michauxii and potaninii derive from the unlatinized personal names Michaux and Potanin. Two kinds of epithets are possible: substantival ones, i.e. nouns, in the genitive case (michauxii, potaninii) and adjectival ones, in the nominative case (michauxianus, potaninianus). Substantival epithets must agree in gender and number with the persons being honoured (masculine or feminine, singular or plural), whereas adjectival epithets must agree in gender with the generic name (masculine, feminine, or neuter, singular). This agreement is achieved by using the appropriate Latin termination. Both kinds of epithets are formed by adding a termination to the unlatinized personal name, with or without minor modifications depending on whether the personal name ends in -a, another vowel (-e, -i, -o, -u, -y), -er, or a consonant (but not -er). These rules are set out in Art. 60.8, but may also be “keyed out” as follows:

Article 60.10 concerns the formation of adjectival epithets that combine elements derived from two or more Greek or Latin words. Epithets not formed in accordance with this rule must be corrected to conform with it, unless Rec. 60G applies (see Pseudocompounds, p. 109). Remember that Art. 60.10 concerns only epithets (not generic names), and only adjectival epithets, and applies only when the elements are derived from Greek or Latin words. For example, in Andromeda polifolia L., the epithet is actually a noun (the pre-Linnaean generic designation “Polifolia”); it is not therefore to be changed to “poliifolia”. This is not apparent without analysis of the protologue. You should always check the protologue in case the derivation is not as you initially assume. The epithet in Tetragonia tetragonoides (Pall.) Kuntze is derived from a noun (the generic name Tetragonia) and a suffix (-oides), not from two Greek or Latin words (a suffix is not a word); it is not therefore to be changed to “tetragonioides”.

A regular compound epithet contains a noun or adjective in a non-final position, e.g. aquilegiifolia, which means Aguilegia-leaved. Aquilegia is a noun in a non-final position. The case ending, -ae, of the genitive singular, Aquilegiae, is removed, giving aquilegi-, to which is added a connecting vowel, -i-, and the ending, -folia.

The connecting vowel is only used before a consonant and is -i- when the elements of the compound are Latin or -o- when they are Greek. Mixed compounds, with one element Latin and the other Greek are discouraged (Rec. 23A.3(c)) but are not errors to be corrected, e.g. we cannot correct the epithet of Chomelia grandicarpa, which compounds Latin for large and Greek for fruit, to the all-Greek macrocarpa.

A pseudocompound contains a noun or adjective in a non-final position as the whole word inflected with a case ending (Rec. 60G.1(b)). For example, the epithet albomarginatus means margined with white. Here album (white) is a noun in a non-final position. It appears as the whole word in the ablative case, albo (implying “with white”), followed by the adjective marginatus (margined).

Under Art. 60.11, the use in a pseudocompound of the genitive singular case ending of a Latin first-declension noun instead of a connecting vowel is treated as an error to be corrected, unless it makes a semantic distinction. For example, the pseudocompound epithet tubaeformis is derived from tuba (trumpet), a Latin first-declension noun, of which the genitive singular is tubae. The regular compound under Art. 60.10 would be tubiformis, but that would be identical with the regular compound tubiformis derived from tubus (tube, genitive singular tubi). Because the epithet tubaeformis makes a semantic distinction between tuba and tubus, it is not an error to be corrected. On the other hand, the genitive singular of Aquilegia, another Latin first-declension noun, is Aquilegiae, which would give “aquilegiaefolia” in a pseudocompound. Because in this case no semantic distinction is being made, the epithet must be corrected to the regular compound form, aquilegiifolia.

Gender

All generic names have a gender: masculine, feminine, or neuter. This is significant because adjectival epithets in the names of subdivisions of genera, species, and infraspecific taxa must agree in gender with the generic name (Art. 21.2, 23.5, and 24.2). If they do not, the names are validly published but the terminations of the epithets are to be corrected without change of the author citation or date of the name (Art. 32.2). Of course, it is quite possible for there to be no adjectival epithets among the names of the subordinate taxa of some small genera.

There are some general trends that are worth remembering. Names ending in -us (e.g. Agaricus, Astragalus) tend to be masculine, unless they are names of trees, in which case they tend to be feminine (Aesculus, Prunus, Quercus, Ulmus). Names ending in -a and -is are nearly always feminine (Rosa, Yucca; Cannabis, Orchis), unless they end in -ma, in which case they tend to be neuter (Alisma, Melastoma). Names ending in -um are always neuter (Allium, Lilium).

The rules on gender are in Art. 62 of the Code. The basic rule is Art. 62.1, which states that a generic name retains the gender assigned by nomenclatural tradition. The gender of nomenclatural tradition usually, but not always, coincides with the classical gender of the corresponding Greek or Latin word, if any, e.g. Quercus L. 1753 is feminine in nomenclatural tradition and the classical gender of the Latin word quercus (oak) is also feminine. If the classical usage of the name or the author’s original usage of the name is different, it does not override the nomenclatural tradition. If there is no nomenclatural tradition, the generic name retains the gender assigned by its original author (also Art. 62.1).

Arbitrarily formed generic names, vernacular names used as generic names, or adjectives used as generic names also take the gender assigned by the original author (Art. 62.3). If that author did not indicate the gender, a subsequent author may choose a gender, and the first such choice, if effectively published, is a nomenclatural act and must be followed.

There are exceptions, which comprise the remaining rules of Art. 62. Compound generic names take the gender of the last word in the nominative case in the compound (Art. 62.2), e.g. the gender of Parasitaxus de Laub. 1972 is feminine because the gender of Taxus L. 1753 is feminine. There are also certain endings of generic names that always take either masculine, feminine, or neuter gender. These are listed in Table 9 alongside the relevant Article numbers.

It is also possible to conserve a name under Art. 14.11 to preserve a particular gender (see Chapter 8).

Table 9.Download as CSV 

Endings of generic names that always take a particular gender.

Masculine	Article	Feminine	Article	Neuter	Article
-anthos	62.2(c)	-achne	62.2(b)	-ceras	62.2(c)
-anthus	62.2(c)	-anthes	62.4	-dendron	62.2(c)
-botrys	62.2(a)	-chlamys	62.2(b)	-nema	62.2(c)
-cheilos	62.2(c)	-daphne	62.2(b)	-stigma	62.2(c)
-chilos	62.2(c)	-glochin	62.2(b)	-stoma	62.2(c)
-chilus	62.2(c)	-mecon	62.2(b)
-codon	62.2(a)	-odes	62.4
-gaster	62.2(b)	-oides	62.4
-ites	62.4	-osma	62.2(b)
-myces	62.2(a)
-odon	62.2(a)
-panax	62.2(a)
-phycos	62.2(c)
-phycus	62.2(c)
-phykos	62.2(c)
-pogon	62.2(a)
-stemon	62.2(a)

Major changes were made to the Code at the Shenzhen Congress of 2017 with respect to the nomenclature of organisms treated as fungi. The two main changes were the decision to move all the provisions of the Code that deal solely with names of fungi to a separate section, Chapter F. The second was that the provisions of Chapter F can be amended only by an International Mycological Congress (IMC), whereas the provisions of the rest of the Code can be amended (as before) only by an International Botanical Congress (IBC). The decisions of the IMC are binding on the subsequent IBC, except that the Editorial Committee can make editorial adjustments (see Chapter 13).

If you are working in mycology, do remember that Chapter F consists of those provisions of the Code that deal solely with names of fungi. But most of the other provisions of the Code deal with names of fungi just as much as they do with names of algae and plants. Therefore, never think that you only need to learn Chapter F. The introduction to Chapter F includes this emphatic reminder as well as an annotated list of particularly relevant provisions in other parts of the Code.

IMCs are held every four years, e.g. 2018, 2022, and 2026, whereas IBCs are held every six years, e.g. 2017, 2023, and 2029. Therefore, one or two IMCs are held between consecutive IBCs. Changes to Chapter F resulting from an IMC that has been held since the previous IBC are shown in the online version of the Code, incorporated in such a way that it is clear that they originated from a specific IMC. A revised version of Chapter F is also published separately in IMA Fungus. The key changes resulting from the San Juan IMC of 2018 were summarized by May & al. (2018) and are also included in the present guide.

A hybrid individual contains genetic material inherited from both parents, as in other sexually produced individuals, but in this case those parents are considered to belong to different taxa. Many taxa are interpreted as hybrids by some scientists but are considered to be non-hybrid taxa by others. Hybridization can be part of the process of evolution, where polyploid hybrids that are able to reproduce eventually lose their extra chromosomes and become diploid species. Such hybrids, which essentially behave like “normal” species, are quite different from the rare occurrences of hybrid individuals in nature, where the parent species coexist, and from artificial hybrids created in cultivation by deliberate crossing of parent species.

The Code provides for hybrids to be expressed in two ways. One is by means of a hybrid formula, e.g. Agrostis × Polypogon, Agrostis stolonifera × Polypogon monspeliensis, and Polypodium vulgare subsp. prionodes × P. vulgare subsp. vulgare. The other way is by means of a hybrid name, e.g. ×Agropogon, ×Agropogon littoralis, and Polypodium vulgare nothosubsp. mantoniae (which correspond with the aforementioned three hybrid formulae, respectively). The provisions for naming hybrids had been placed in Appendix I in several previous editions of the Code, but in the Shenzhen Code they form Chapter H.

Be aware of an important rule (Art. H.3.2): a hybrid taxon cannot be designated unless at least one parent taxon is known or can be postulated. If you have a new taxon that you suspect may be a hybrid, but you cannot postulate even one parent, you cannot describe it as a hybrid taxon. You can, however, describe it as a regular, non-hybrid taxon.

Some of the rules for naming hybrids apply primarily to cultivated organisms, e.g. hybrids between three or more genera (especially common in the Orchidaceae). Names of hybrid genera need only be effectively published with a statement of parentage, and no validating description or diagnosis or type is required. The rules become more complex when naming hybrids between subdivisions of genera or infraspecific taxa, especially when the (putative) parents are taxa at different ranks.

My own preference is to refrain from publishing hybrid names unless the hybrid occurs frequently in nature and is repeatedly produced by its parents crossing or is itself able to reproduce. Publishing a hybrid name when only one or a few individuals are known, especially if the hybrid is unable or unlikely to reoccur or reproduce or exists only in cultivation, seems unnecessary to me, perhaps even unscientific. A hybrid formula, although somewhat more cumbersome, avoids the need to comply with the often complex rules on publishing hybrid names, and it is anyway more informative because it communicates the known or postulated parentage.

A brief summary of the main rules on names of hybrids is provided below. Full details can be found in Chapter H.

• Indicating a hybrid. A hybrid is indicated by use of the multiplication sign (×) or by addition of the prefix “notho-” or “n-” (from Greek νόθος, nothos, hybrid) to the rank-denoting term of the taxon (Art. H.1.1), e.g. nothovar., nothosubsp., nothosect.
• Ranks of nothotaxa. The principal ranks of nothotaxa (hybrid taxa) are nothogenus and nothospecies. These ranks are the same as genus and species (Art. 3.2). The subordinate ranks of nothotaxa are the same as the subordinate ranks of non-hybrid taxa, except that nothogenus is the highest rank permitted (Art. 4.4). The appropriate rank of a nothotaxon is that of its parent taxa, or, if their ranks are unequal, it is the lowest of those ranks (Art. H.5).
• Hybrid formulae. A hybrid may be expressed by means of a hybrid formula in which a multiplication sign (×) is placed between the names of the parent taxa (Art. H.2.1). Formulae designating hybrids are not to be regarded as species names (Art. 23.6(d)).
• Hybrid names. Alternatively, a hybrid may receive a name (Art. H.3.1), which must be validly published.
• Nothogenera and subdivisions of nothogenera. In order to be validly published, the name of a nothotaxon at the rank of genus or subdivision of a genus must be effectively published with a statement of the names of the parent genera or subdivisions of genera (Art. H.9.1). No description or diagnosis is necessary, nor is a type necessary. The name or epithet is termed a “condensed formula”, which combines elements from two or more generic names or subdivisional epithets that are correct for the parent taxa, e.g. ×Agropogon for hybrids betweenAgrostis and Polypogon, orPtilostemon nothosect. Platon for hybrids betweenP. sect . Platyrhaphium andP. sect. Ptilostemon (Art. H.6–H.8).
• Nothospecies and infraspecific nothotaxa. In order to be validly published, the name of a nothotaxon at the rank of species or below must comply with the same rules as names of non-hybrid taxa of the same rank (Art. 32.4 and H.10.1). In addition, at least one parent taxon must be known or postulated (Art. H.3.2).
• Priority. Names given to hybrids are subject to the same rules on priority as are those of non-hybrid taxa of equivalent rank (Art. 11.9).
• Homonymy and synonymy between hybrids and non-hybrids. For purposes of homonymy and synonymy the multiplication sign and the prefix “notho-” are disregarded (Art. H.3.3), e.g. ×Hordelymus Bachteev & Darevsk. 1950 is a later homonym of Hordelymus (Jess.) Harz 1885; the names apply to a nothogenus and a non-hybrid genus, respectively. Note that the first name is a condensed formula (Art. H.6), but the latter is not. Just because a generic name resembles a condensed formula does not necessarily mean it is a nothogeneric name.
• Transfer between hybrid and non-hybrid categories. When a taxon at the rank of species or below is transferred from the non-hybrid category to the hybrid category of the same rank, or vice versa, the author citation remains unchanged but may be followed by an indication in parentheses of the original category, e.g. Stachys × ambigua Sm. (pro sp.), Salix glaucops Andersson (pro hybr.), where the abbreviations stand for pro specie and pro hybrida, “as species” and “as hybrid”, respectively (Art. 50.1).

For precision while discussing several codes in this section, and to avoid having to repeat its long title, I will refer to the International Code of Nomenclature for algae, fungi, and plants as the Shenzhen Code.

Nomenclatural starting-point for algae (with exceptions; Art. 13.1(e)), bryophytes (Sphagnaceae and Hepaticae, including Anthocerotae; Art. 13.1(c)), fungi (Art. F.1.1), and vascular plants (Art. 13.1(a)). Species plantarum, ed. 1 (Linnaeus, 1753). No names published before a nomenclatural starting-point are validly published.

Nomenclatural starting-point for suprageneric names of vascular plants (Art. 13.1(a)) and certain bryophytes (Sphagnaceae and Hepaticae, including Anthocerotae; Art. 13.1(c)). Genera plantarum (Jussieu, 1789).

Nomenclatural starting-point for bryophytes (Musci, except Sphagnaceae; Art. 13.1(b)). Species muscorum frondosorum (Hedwig, 1801).

Nomenclatural starting-point for fossils (Art. 13.1(f)). Versuch … der Flora der Vorwelt, Heft 1 (Sternberg, 1820).

Nomenclatural starting-point for certain algae (Desmidiaceae; Art. 13.1(e)). The British Desmidieae (Ralfs, 1848).

Nomenclatural starting-point for certain algae (Nostocaceae heterocysteae; Art. 13.1(e)). “Révision des Nostocacées hétérocystées” (Bornet & Flahault, 1886–1888).

Indication of suprageneric rank. The termination of a suprageneric name published on or after 1 January 1887 is acceptable as an indication of the rank (Art. 37.2) (e.g. -aceae indicates the rank of family, -eae that of tribe), although any explicitly designated rank takes precedence and the rules on rank sequence (Art. 5.1 and 37.6–37.8) apply. Before 1887, such terminations cannot indicate rank.

Variety is default infraspecific rank. If a publication before 1890 uses only one infraspecific rank, that rank is considered to be variety unless the author indicates otherwise. It was common in these early publications to cite infraspecific taxa without using a rank-denoting term, e.g. “β. glabra”, “γ. intermedia” (Art. 37.4). Publications from 1890 onward generally indicate the rank; if they do not, the names are validly published but unranked (but only before 1 January 1953, see there).

Nomenclatural starting-point for certain algae (Nostocaceae homocysteae; Art. 13.1(e)). “Monographie des Oscillariées” (Gomont, 1892–1893).

Nomenclatural starting-point for certain algae (Oedogoniaceae; Art. 13.1(e)). “Monographie und Iconographie der Oedogoniaceen” (Hirn, 1900).

Illustration with analysis. Certain names of new taxa published before 1908 may be validly published even if only accompanied by an illustration with analysis, i.e. without a written description or diagnosis or reference to such (Art. 38.7 and 38.8; for analysis see Art. 38.9 and 38.10). Such names published on or after 1 January 1908 are not validly published.

Latin technical terms as generic names. The name of a new genus published before 1912 may coincide with a Latin technical term in use in morphology at the time of publication (e.g. Radicula, Tuber), provided that it was accompanied by a species name published in accordance with the binary system of Linnaeus (Art. 20.2), i.e. a binomial species name. Such names published on or after 1 January 1912 are not validly published.

Validating illustration for names of fossil-taxa. A validating illustration, or reference to such, is required for valid publication on or after 1 January 1912 of a name of a new fossil-taxon at the rank of genus or below (Art. 43.2). A validating illustration is an illustration or figure showing the essential characters.

Largely mechanical method of type selection. A publication that appeared before 1921 has adopted a largely mechanical method of type selection if any of the criteria given in Art. 10.7(c–f) apply; likewise for a publication that appeared before 1935 if either of the criteria given in Art. 10.7(a and b) applies; but if the authors specifically stated that they did not use such a method, that statement is to be accepted.

Latin requirement for names of fungi and plants. A name of a new taxon of fungi or plants (not of algae or fossils) published between 1 January 1935 and 31 December 2011, inclusive, is not validly published unless accompanied by a Latin description or diagnosis or by a reference to such (Art. 39.1). That reference may be indirect prior to 1953 but must be full and direct on or after 1 January 1953 (see there).

Effective publication. The following kinds of material issued on or after 1 January 1953 are not effectively published: indelible autograph (Art. 30.5), trade catalogues and non-scientific newspapers (Art. 30.7), printed matter accompanying specimens (Art. 30.8), and certain theses submitted to a university or other institute of education for the purpose of obtaining a degree (Art. 30.9).

Alternative names. Alternative names published on or after 1 January 1953 are not validly published (Art. 36.3). In this sense, they are defined as two or more different names based on the same type and accepted as alternatives simultaneously for the same taxon by the same author in the same publication. This is a different sense to the alternative family names authorized by Art. 18.6.

Indication of rank. A name published on or after 1 January 1953 is not validly published unless there is a clear indication of the rank of the taxon concerned (Art. 37.1). Such a name published before 1953 is validly published but unranked (Art. 37.3).

Full and direct reference to basionym or replaced synonym. A new combination, name at new rank, or replacement name published on or after 1 January 1953 is not validly published unless the reference to the basionym or replaced synonym is full and direct (Art. 41.5, see also Art. 41.6 and 41.8), whereas for names published before 1953 the reference may be either direct or indirect (Art. 41.3, see also Art. 41.4).

Full and direct reference to earlier description or diagnosis. When the protologue of a name of a new taxon includes no description or diagnosis of the taxon, it may instead refer to a previously and effectively published description or diagnosis (Art. 38.1(a)). If the name is published on or after 1 January 1953, that reference must be full and direct, otherwise the name is not validly published, whereas for names published before 1953 the reference may be either direct or indirect (Art. 38.13).

Determining date of conservation or protection of a name. Before 1954, conservation of a name takes effect on the date of the decision on the conservation proposal by the relevant International Botanical Congress (Art. 14.15, for the dates see Art. 14 Note 4). On or after 1 January 1954, conservation or protection of a name takes effect on the date of effective publication of the General Committee’s approval of the conservation or protection proposal (Art. 14.15).

Indication of type. A name of a new taxon at the rank of genus or below published on or after 1 January 1958 is not validly published unless the type of the name is indicated (Art. 40.1).

Validating illustration for names of algae. A validating illustration, or reference to such, is required for valid publication on or after 1 January 1958 of a name of a new taxon of algae (except fossils) at the rank of species or below (Art. 44.2). A validating illustration is an illustration or figure showing the distinctive morphological features.

Latin requirement for names of algae. A name of a new taxon of algae (except fossils) published between 1 January 1958 and 31 December 2011, inclusive, is not validly published unless accompanied by a Latin description or diagnosis or by a full and direct reference to such (Art. 44.1).

Effective publication. Seed-exchange lists issued on or after 1 January 1973 are not effectively published (Art. 30.7).

Requirements for valid publication not simultaneously fulfilled. For a name to be validly published on or after 1 January 1973 without simultaneous fulfilment of all the relevant requirements of the Code for valid publication, a full and direct reference must be given to the places where these requirements were previously fulfilled (Art. 33.1). Before 1973, such a name is validly published when the last of these requirements is fulfilled.

Writing “typus” or “holotypus”. Indication on or after 1 January 1990 of the type of a name of a new taxon at the rank of genus or below must include one of the words “ typus” or “ holotypus”, or its abbreviation, or its equivalent in a modern language (Art. 40.6). Otherwise the name is not validly published.

Specifying herbarium of holotype. Indication on or after 1 January 1990 of a specimen or unpublished illustration as the holotype of a name of a species or infraspecific taxon must specify the single herbarium, collection, or institution in which the type is conserved (Art. 40.7). Otherwise the name is not validly published.

Specifying herbarium of lectotype, neotype, or epitype. Designation on or after 1 January 1990 of a specimen or unpublished illustration as the lectotype or neotype of a name of a species or infraspecific taxon must specify the herbarium, collection, or institution in which the type is conserved (Art. 9.22). The same applies to an epitype (Art. 9.21), which entered the Code at the Tokyo Congress of 1993. Failure to comply with these rules results in an ineffective type designation.

Latin or English requirement for names of fossil-taxa. A name of a new fossil-taxon published on or after 1 January 1996 is not validly published unless accompanied by a Latin or English description or diagnosis or by a full and direct reference to such (Art. 43.1).

Writing “lectotypus”, “neotypus”, or “epitypus”. Designation on or after 1 January 2001 of the lectotype, neotype, or epitype of a name of a species or infraspecific taxon must use the word “ lectotypus”, “ neotypus”, or “ epitypus”, its abbreviation, or its equivalent in a modern language (Art. 9.23). Otherwise the type designation is ineffective.

Writing “designated here”. Designation on or after 1 January 2001 of a lectotype, neotype, or epitype must include the phrase “designated here” (hic designatus) or an equivalent (Art. 7.11). The same applies to the equivalent designation of the type of a name of a genus or subdivision of a genus; it does not apply to indicating the type of a name of a new taxon. Failure to comply with this rule results in an ineffective type designation.

Identifying validating illustrations as the type. A name of a new fossil-taxon at the rank of species or below published on or after 1 January 2001 is not validly published unless at least one of the validating illustrations is identified as representing the type specimen (Art. 43.3). When, before 2001, a type specimen is indicated in the protologue but not identified among the validating illustrations, a lectotype must be designated from among the specimens illustrated in the protologue (Art. 9.15).

Illustrations as types. The type of a name of a new taxon (except fossils) at the rank of species or below published before 2007 may be an illustration. For such a name to be validly published on or after 1 January 2007, the type must be a specimen (except under certain circumstances for non-fossil microscopic algae and non-fossil microfungi) (Art. 40.4 and 40.5).

Citing the basionym or replaced synonym. A new combination, name at new rank, or replacement name published on or after 1 January 2007 is not validly published unless its basionym or replaced synonym is cited (Art. 41.5). This means the basionym or replaced synonym must actually appear in the text; merely indicating it, e.g. by citing only its author and place of publication, is not enough.

Latin or English requirement now universal. A name of a new taxon (of algae, fungi, or plants, whether fossil or non-fossil) published on or after 1 January 2012 is not validly published unless accompanied by a Latin or English description or diagnosis or by a full and direct reference to such (Art. 39.2). (Already the case for names of fossil-taxa from 1 January 1996.)

Effective electronic publication. Electronic material distributed on or after 1 January 2012 is effectively published provided that it is in Portable Document Format (PDF) in an online publication with an International Standard Serial Number (ISSN) or an International Standard Book Number (ISBN) (Art. 29.1). Electronic material distributed before 2012 is not effectively published (Art. 29 Note 1).

Registration of names of fungi. Names of organisms treated as a fungi (including fossil fungi) published on or after 1 January 2013 are not validly published unless the identifier (i.e. an identification number or code) issued for the name by a recognized repository is cited in the protologue (Art. F.5.1). This includes names of new taxa, new combinations, names at new ranks, and replacement names.

Names of fungi with a pleomorphic life cycle. A name of non-lichen-forming Ascomycota or Basidiomycota published before 2013 for a particular sexual state of a fungus is protected from being illegitimate under Art. 52, if it was nomenclaturally superfluous when published because the protologue included a type referable to a different sexual state (Art. F.8.1).

Cultures as types. The type specimen of an algal or fungal name may be a culture, provided it is preserved in a metabolically inactive state (Art. 8.4). A name of a new species or infraspecific taxon published on or after 1 January 2019 with such a type is not validly published unless the protologue includes a statement that the culture is preserved in a metabolically inactive state (Art. 40.8).

Registration of type designations for fungal names. Designation on or after 1 January 2019 of the lectotype, neotype, or epitype of a name of an organism treated as a fungus (including fossil fungi) must cite the identifier issued for the typification by a recognized repository (Art. F.5.4). The same applies to the equivalent designation of the type of a name of a genus or subdivision of a genus. Failure to comply with this rule results in an ineffective type designation.

Fungal homonyms. A name of a taxon treated as a fungus (including fossil fungi) published on or after 1 January 2019 is illegitimate if it is a later homonym of a prokaryotic or protozoan name (Art. F.6.1).

Anyone may submit proposals to amend the Code to the journal Taxon or proposals to amend Chapter F to the journal IMA Fungus. The published proposals are voted on by the international nomenclature user community, ultimately by an IBC or an IMC. The Code (except Chapter F) may be modified only by action of a plenary session of an IBC on a resolution moved by the Nomenclature Section of that IBC. Chapter F may be modified only by action of a plenary session of an IMC on a resolution moved by the Fungal Nomenclature Session of that IMC.

At least three years before the IBC, a notice is placed in Taxon announcing that the column “Proposals to amend the Code” is open (for the Shenzhen IBC, see Turland & Wiersema, 2013). These proposals are not subject to peer-review, but the column editors, who in recent years have been the Rapporteur-général and Vice-rapporteur, work closely with the proposers to edit proposals, ensuring that they are logical, and pointing out any consequences that the proposers may not have foreseen. Proposals may be withdrawn by the proposers if, during the editorial process, unwanted consequences become apparent. The closing date for proposals is about one year before the IBC. After the last of the proposals has been published, the Rapporteur-général and Vice-rapporteur compile a synopsis of proposals, including their comments, also published in Taxon (for the Shenzhen IBC, see Turland & Wiersema, 2017). A preliminary guiding vote is held early in the year of the IBC. In order to participate in the guiding vote, you must be either (1) an author of at least one proposal to amend the Code, or (2) an individual member of the International Association for Plant Taxonomy, or (3) a member of one of the Permanent Nomenclature Committees. The purpose of the guiding vote is to advise the Nomenclature Section of the IBC of the level of support for the proposals, and the results of the vote are made available to the Section (e.g. by publication in Taxon, see Turland & al., 2017a).

When preparing a proposal, you should be careful to distinguish between what the Code actually says and what you think it should say. There will normally be a difference, and this will be the basis of your proposal. Think carefully about the logic of your proposal, and try to anticipate all side-effects; deal with the side-effects appropriately. Remember that changes to the Code are retroactive to 1753 unless limited by date (Principle VI). In other words, a new rule will behave as if it had always been in the Code (and the Code behaves as if it had existed since 1753). Be concise in your arguments. Lengthy justifications may need to be published in a separate (and peer-reviewed) paper in Taxon. Be realistic as to whether the international scientific community is likely to agree with you. Members of that community tend to be conservative when contemplating changes to the rules of nomenclature. If your proposal is radical, you will need to be very persuasive indeed—or make it less radical. Not only does it have to avoid receiving 75% or more “no” votes in the preliminary guiding vote, but it must survive discussion and be accepted at the Nomenclature Section.

The format of recent IBCs has been a main week of plenary lectures, symposia, workshops, etc., with the Nomenclature Section taking place in the immediately preceding week. Whereas thousands of people might attend the main week of the IBC, typically only 100–300 attend the Nomenclature Section. In order to be a member of the Nomenclature Section with the right to vote on proposals, you need to be a registered member of the IBC (no qualifications are required, just a fee) and to attend in person.

The Nomenclature Section is run by the Bureau of Nomenclature, which consists of the President of the Nomenclature Section, up to five Vice-presidents, the Rapporteur-général, the Vice-rapporteur, and the Recorder. The President chairs the proceedings, the Vice-presidents serve in place of the President if requested, the Rapporteur-général and Vice-rapporteur provide the expertise on the Code, and the Recorder handles logistics and ensures that the discussions and decisions are recorded in detail. These officers are either elected or appointed: the President is elected by the General Committee, the Vice-presidents are appointed by the Bureau of Nomenclature, the Rapporteur-général is elected by the previous IBC, the Vice-rapporteur is appointed by the Rapporteur-général and approved by the General Committee, and the Recorder is appointed by the Organizing Committee of the IBC.

The main task of the Nomenclature Section is to discuss, amend if necessary, and vote on proposals to amend the Code. In addition, the recommendations of the General Committee on the previous six years of proposals to conserve, protect, or reject names, to suppress works, and requests for binding decisions are subject to approval by the Section.

Each member has one personal vote and may also carry up to 14 institutional votes. Institutions are each allocated between one and seven institutional votes, which may be exercised at the Nomenclature Section by the member who is the authorized delegate of the institution(s). The number of votes allocated to an institution depends on its level of taxonomic activity, e.g. number of active staff, size of collections, and current publications. The list of institutions and numbers of allocated votes is revised prior to each IBC by the Committee on Institutional Votes, subject to approval by the General Committee. An institution wishing to vote for the first time, or to increase or decrease its allocated votes, may contact the Rapporteur-général (who serves as chair of the Committee on Institutional Votes) with relevant information on taxonomic activity.

A qualified majority (at least 60%) of votes cast at the Nomenclature Section is required to accept a proposal or refer it to the Editorial Committee, and thereby effect a change to the Code. Recommendations of the General Committee can be rejected by the same qualified majority; otherwise they are accepted. The Section may also refer proposals to a Special-purpose Committee (see p. 145). Proposals that receive 75% or more “no” votes in the preliminary guiding vote are automatically rejected, and proposals that concern only Examples or the Glossary are automatically referred to the Editorial Committee, although in both cases a proposal may be reintroduced for discussion. Proposals may also be amended during discussion.

The Nomenclature Section also elects a Nominating Committee at the proposal of the President. The Nominating Committee prepares a report proposing the Rapporteur-général for the next IBC and the members of the Permanent Nomenclature Committees to serve until the next IBC (except the Nomenclature Committee for Fungi, which is elected by the IMC).

The decisions of the Nomenclature Section become a resolution of the IBC, ratified at a plenary session (normally the closing ceremony on the last day of the IBC), at which point the Section’s decisions become official and the rules of the new Code take effect unless expressly limited by date. After the IBC, a report is published in Taxon detailing all the decisions and appointments made by the Section (that for the Shenzhen IBC was published 16 days after the closing ceremony, Turland & al., 2017b).

The audio recordings of the discussions of the Nomenclature Section are transcribed into text and then edited, with the help of the published report and written records made at the Section, to produce a full report of the nomenclature proceedings of the IBC. The full reports for the Vienna and Melbourne IBCs were published online, as open-access volumes of PhytoKeys (Flann & al., 2014, 2015). That for the Shenzhen IBC is currently being prepared.

As mentioned earlier, Chapter F of the Code may be modified only by an IMC, whereas the rest of the Code may be modified only by an IBC. The procedure for modifying Chapter F is very similar to that described above, but the timetable is tighter because the IMC is held every four years, while the IBC is held every six years. Proposals to amend Chapter F are submitted to and published in the journal IMA Fungus. There is a synopsis of proposals (May & Redhead, 2018) and a preliminary guiding vote (May & Miller, 2018). The IMC has a Fungal Nomenclature Session (not “Section”). This took place during one day at the San Juan IMC of 2018. The much shorter duration was possible because there were far fewer proposals to consider (only 18 compared with 397 at the Shenzhen IBC). There is a Fungal Nomenclature Bureau consisting of the Chair, Deputy Chairs, Secretary, Deputy Secretary, and Recorder (Chair and Secretary are equivalent to President and Rapporteur-général, respectively). The Rapporteur-général for the next IBC is invited to attend the Session as a non-voting advisor. There are no institutional votes. The Session considers and votes on proposals to amend Chapter F and can authorize Special-purpose Committees. The Session does not vote on recommendations of the General Committee; this is done only at the IBC. The Session elects the Secretary for the next IMC and the members of the Nomenclature Committee for Fungi, who have been proposed by the Nominating Committee of the Fungal Nomenclature Session. After the IMC, a report is published in IMA Fungus detailing the decisions and appointments made by the Fungal Nomenclature Session (for the San Juan IMC, see May & al., 2018). The San Juan IMC established an ad hoc Editorial Committee for Fungi to prepare the new edition of Chapter F and work with the regular Editorial Committee to finalize and approve it before publication.

A significant portion of the work in managing the Code, including considering proposals to conserve, protect, or reject names, and the actual editing of the Code, is delegated to Permanent Nomenclature Committees. They are as follows:

The Nomenclature Section of an IBC can authorize Special-purpose Committees to investigate and discuss complex issues. This may stem from a particular proposal or set of proposals that cannot be resolved at the Section. The General Committee appoints the membership of the Special-purpose Committee, which (if all goes well) eventually reports with proposed solutions to the Nomenclature Section of the next IBC, often by publishing in Taxon a report and/or proposals to amend the Code. For example, three consecutive Special-purpose Committees to investigate electronic publication were established at the Tokyo, Saint Louis, and Vienna IBCs. The proposals of the first two Committees were rejected by the Saint Louis IBC in 1999 and the Vienna IBC in 2005, but those of the third were accepted by the Melbourne IBC in 2011, permitting certain electronic material to be effectively published under the Code. Two of the Special-purpose Committees established at the Melbourne IBC resulted in the new Division III of the Shenzhen Code and greater autonomy in the governance of fungal nomenclature, i.e. the creation of Chapter F and the authority of the Fungal Nomenclature Session of the IMC to amend it. The Special-purpose Committees established by the Shenzhen IBC, together with their mandates and members, were announced by Wilson (2019). The Fungal Nomenclature Session of an IMC also has the power to authorize Special-purpose Committees, which are appointed by the Nomenclature Committee for Fungi. Two were established by the San Juan IMC of 2018.

Linnaeus himself drew up a set of 365 principles that dealt to some extent with biological nomenclature, the Fundamenta botanica (Linnaeus, 1735), but these mostly died with their creator and are now forgotten. Early in the following century, Augustin Pyramus de Candolle put forward the principle of priority in his Théorie élémentaire de la botanique (Candolle, 1813). However, a formal set of rules for the nomenclature of algae, fungi, and plants did not come into being until more than half a century later when Alphonse de Candolle, son of Augustin Pyramus, published his Lois de la Nomenclature Botanique (Candolle, 1867). Candolle’s Lois (Laws) were prepared at the request of the Organizing Committee of the International Botanical Congress held in Paris in 1867, to serve as a basis for discussions on controversial issues in nomenclature.

The next set of rules, based on Candolle’s Lois, were the Règles Internationales de la Nomenclature Botanique (International Rules of Botanical Nomenclature) produced at the II International Botanical Congress, held in Vienna in 1905 (Briquet, 1906). However, trouble was brewing. In the first decade of the 20th century, many scientists in the United States became frustrated by what they perceived as their European colleagues’ sluggishness in adopting the type method, and were unhappy at what they saw as the arbitrariness of permitting so many exceptions to the rules through the conservation of numerous generic names at the Vienna Congress of 1905 (see Briquet, 1906: 72–93). They therefore decided to take a separate path and adopt their own set of rules, first the so-called “Philadelphia Code” (Arthur & al., 1904) and then the American Code of Botanical Nomenclature (Arthur & al., 1907). The next Congress, held in Brussels in 1910, produced a new edition of the Règles (Briquet, 1912), but the schism between it and the American Code persisted. The London Congress scheduled for 1915 was cancelled because of World War I. At the next Congress, held in Ithaca in 1926, J.I. Briquet, the Rapporteur-général at the Vienna and Brussels Congresses, introduced a round-table discussion on nomenclature (Section for Taxonomy, 1929) and A.S. Hitchcock made suggestions for reconciliation in a paper on the relevance of nomenclature to taxonomy (Hitchcock, 1929). The schism between much of the United States and the rest of the world ended in 1930, when the Cambridge Congress adopted the type method and produced the International Rules of Botanical Nomenclature (Briquet, 1935).

The Amsterdam Congress of 1935 did not produce an official revised set of International Rules, but there were unofficial “Brittonia Rules” (Camp & al., 1947) and a belated supplement to the previous Cambridge Rules (Sprague, 1950). The first International Code of Botanical Nomenclature (ICBN) was adopted by the Stockholm Congress of 1950 (Lanjouw & al., 1952). Since then, there have been ten further decreasingly ambiguous and increasingly detailed editions of the International Code of Botanical Nomenclature, followed by two editions of the International Code of Nomenclature for algae, fungi, and plants, each Code adopted by each subsequent Congress and superseding all previous editions.

Table 11.Download as CSV 

International Botanical Congresses (IBC) and associated editions of the Code.

IBC no.	IBC year	City	Rapporteur-général	Vice-rapporteur	Code reference	Code year
–	1867	Paris	Candolle, A.L.P.P. de (1806–1893) (Rapporteur)	–	Lois de la Nomenclature Botanique (Candolle, 1867)	1867
I	1900	Paris	–	–	Decision to revise the rules of botanical nomenclature at the next (Vienna) Congress, with John Briquet in charge (Perrot, 1900: 453–463)	–
II	1905	Vienna	Briquet, J.I. (1870–1931) (first Rapporteur-général)	–	Règles Internationales de la Nomenclature Botanique (Briquet, 1906)	1906
–	–	–	–	–	“Philadelphia Code” (Arthur & al., 1904), followed by American Code of Botanical Nomenclature (Arthur & al., 1907)	1904, 1907
III	1910	Brussels	Briquet, J.I.	Harms, H.A.T. (1870–1942) (first Vice-rapporteur)	Règles Internationales de la Nomenclature Botanique (Briquet, 1912)	1912
–	1915	London	–	–	Congress cancelled because of World War I	–
IV	1926	Ithaca	–	–	No Rules/Code published, but there was a round-table discussion on botanical nomenclature (Section for Taxonomy, 1929) and a paper on the relevance of nomenclature to taxonomy (Hitchcock, 1929)	–
V	1930	Cambridge	Briquet, J.I.	Harms, H.A.T.	International Rules of Botanical Nomenclature (Briquet, 1935)	1935
VI	1935	Amsterdam	Sprague, T.A. (1877–1958)	Harms, H.A.T.	No official Amsterdam Rules/Code published, but there were unofficial “Brittonia Rules” (Camp & al., 1947) and a belated supplement to the Cambridge Rules (Sprague, 1950)	1947, 1950
VII	1950	Stockholm	Lanjouw, J. (1902–1984)	Jonker, F.P. (1912–1995)	International Code of Botanical Nomenclature (Lanjouw & al., 1952)	1952
VIII	1954	Paris	Lanjouw, J.	Stafleu, F.A. (1921–1997)	International Code of Botanical Nomenclature (Lanjouw & al., 1956)	1956
IX	1959	Montreal	Lanjouw, J.	Stafleu, F.A.	International Code of Botanical Nomenclature (Lanjouw & al., 1961)	1961
X	1964	Edinburgh	Lanjouw, J.	Stafleu, F.A.	International Code of Botanical Nomenclature (Lanjouw & al., 1966)	1966
XI	1969	Seattle	Stafleu, F.A.	Voss, E.G. (1929–2012)	International Code of Botanical Nomenclature (Stafleu & al., 1972)	1972
XII	1975	Leningrad	Stafleu, F.A.	Voss, E.G.	International Code of Botanical Nomenclature (Stafleu & al., 1978)	1978
XIII	1981	Sydney	Voss, E.G.	Greuter, W. (1938–)	International Code of Botanical Nomenclature (Voss & al., 1983)	1983
XIV	1987	Berlin	Greuter, W.	McNeill, J. (1933–)	International Code of Botanical Nomenclature (Greuter & al., 1988)	1988
XV	1993	Tokyo	Greuter, W.	McNeill, J.	International Code of Botanical Nomenclature (Greuter & al., 1994)	1994
XVI	1999	Saint Louis	Greuter, W.	Hawksworth, D.L. (1946–)	International Code of Botanical Nomenclature (Greuter & al., 2000)	2000
XVII	2005	Vienna	McNeill, J.	Turland, N.J. (1966–)	International Code of Botanical Nomenclature (McNeill & al., 2006)	2006
XVIII	2011	Melbourne	McNeill, J.	Turland, N.J.	International Code of Nomenclature for algae, fungi, and plants (McNeill & al., 2012)	2012
XIX	2017	Shenzhen	Turland, N.J.	Wiersema, J.H. (1950–)	International Code of Nomenclature for algae, fungi, and plants (Turland & al., 2018)	2018
XX	2023	Rio de Janeiro	Turland, N.J.	to be appointed	–	–

Most of the books that traditionally have been the mainstay of biological nomenclature are now freely available online, and these are dealt with on pp. 152–155. This is, of course, immensely convenient for users with adequate access to the internet. Paper books are often expensive for institutions or individuals to purchase or they may require long-distance visits to specialist libraries.

International Code of Nomenclature for algae, fungi, and plants or Shenzhen Code (Turland & al., 2018). Obviously the primary book is the current edition of the Code itself. The printed version is published by Koeltz Botanical Books (http://www.koeltz.com/product.aspx?pid=212180), the online version is hosted by the International Association for Plant Taxonomy (see p. 152).

Other books of great utility include the following (arranged alphabetically by title):

A primer of botanical Latin with vocabulary (Short & George, 2013). Although Botanical Latin has been the standard reference work for more than 50 years, it is not an easy starting point for those without prior knowledge of Latin. This primer, which is cross-referenced to Botanical Latin, has a more informal style, including sections on grammar, exercises, translating, and a 175-page vocabulary of Latin and English words; you can supplement it with Botanical Latin when you want to know even more.

Botanical Latin , now in its 4th edition (Stearn, 1992), with a Spanish translation, Latín botánico (Stearn, 2006), contains practically everything one could ever need to know about the use of the Latin language in systematics. It will enable the reader to translate Latin descriptions and diagnoses of taxa into English (or Spanish), and vice versa, and it contains an extensive Latin and English (and Spanish) vocabulary that reveals the meaning of many technical terms and descriptive epithets of scientific names.

Botanico-periodicum-huntianum, ed. 2. Whereas TL-2 (see below) deals with books, journals are dealt with by BPH-2, or Botanico-periodicum-huntianum, ed. 2 (Bridson & al., 2004). The entries provide a comprehensive listing of almost all “periodicals with botanical content”, a standard abbreviation for each journal title, the ranges of volume numbers and dates of the journals, and any preceding or superseding titles in a series. BPH-2 consists of two volumes (A–M and N–Z) and is also available online (see p. 154).

Fossilium catalogus II: plantae . The index for plant fossils, a serial publication running from Pars 1 in 1913 to the most recent Pars 114 in 2016. It remains at present in printed form only, except for Pars I to Pars X, which are available online (see p. 153).

Index kewensis . Printed catalogues of scientific names have largely been replaced by online databases in recent years. For example, the Index kewensis (Jackson, 1895) and its 21 supplements up to Supplement XXI (Challis & Davies, 2002) include most names of genera and species of seed plants published between 1753 and 2000. Finding names in these catalogues could be a slow process because it was often necessary to check several volumes, e.g. if you were publishing the name of a new species and wanted to be sure that name had never been used before. Today all of this information is searchable online via the International Plant Names Index (IPNI; see p. 153), which should be used in preference to the printed catalogues because not only is the database much more up to date but the information is fuller and very many errors have been corrected.

Order out of chaos . A profoundly useful book is Order out of chaos: Linnaean plant names and their types (Jarvis, 2007). The first part of the book provides a very detailed account of Linnaeus’s materials and methods and explains the process of choosing types to enable the precise application of Linnaean names. The second part is a catalogue of the 9000 or so names of species and varieties published by Linnaeus, with their types. The catalogue is also available online (see p. 154), with links to images of many of the type specimens.

Taxonomic literature, ed. 2 and its supplements, commonly called “TL-2”, includes a huge amount of information on thousands of works published between 1753 and 1940 (including some pre-Linnaean materials). It is arranged by author, giving standard abbreviations of titles, precise dates of publication, location of copies, authors’ biographical details and location of their herbarium specimens including types. The first seven volumes (Stafleu & Cowan, 1976–1988) cover authors from A to Z; then eight supplementary volumes (Stafleu & Mennega, 1992–2000; Dorr & Nicolson, 2008–2009) provide additional information on authors from A to G. TL-2 is also available online (see p. 154).