PREFACE

The rules that govern the scientific naming of algae, fungi, and plants are revised at the Nomenclature Section of an International Botanical Congress (IBC). This edition of the International Code of Nomenclature for algae, fungi, and plants embodies the decisions of the XX IBC, which took place in Madrid, Spain in July 2024. This Madrid Code supersedes the Shenzhen Code (Turland & al. in Regnum Veg. 159. 2018), published seven years ago after the XIX IBC in Shenzhen, China; like its six predecessors, it is written entirely in (British) English. The Shenzhen Code was translated into Chinese, French, Japanese, Portuguese, and Spanish, and it is likely that the Madrid Code, too, will become available in several languages. In questions about the meaning of provisions in translated editions of this Code, the English edition is definitive.

Amending the Code – from Shenzhen to Madrid

Altogether, 433 numbered proposals to amend the Shenzhen Code were published in Taxon, the journal of the International Association for Plant Taxonomy (IAPT), between 31 July 2020 and 27 October 2023. A “Synopsis of proposals”, with comments by the Rapporteur-général and Vice-rapporteur, was published on 21 February 2024 (Turland & Wiersema in Taxon 73: 325–404. 2024) and served as the basis for the preliminary guiding vote (“mail vote”) cast by members of the IAPT, authors of the proposals, and members of the Permanent Nomenclature Committees, as specified in Division III of the Shenzhen Code. Tabulation of the mail vote was handled at the IAPT Secretariat in Bratislava, Slovakia by Eva Kráľovičová and Matúš Kempa. The results were published on 4 July 2024 ahead of the Nomenclature Section (Turland & al. in Taxon 73: 1096–1109. 2024).

The Nomenclature Section met from Monday to Friday, 15–19 July 2024 in the conference hall of the central campus main building of the Consejo Superior de Investigaciones Científicas (CSIC) at Calle de Serrano 117, Madrid 28006, Spain (and was followed, from 21–27 July, by the main part of the IBC at the North Convention Centre of IFEMA Madrid). At the Section, 173 registered members were in physical attendance, carrying 433 institutional votes (from 192 institutions) in addition to one personal vote each, making a total of 606 possible votes. The Section was also livestreamed on the internet, permitting observation of the proceedings but not interactive commenting or voting, with a total of 219 unique users accessing the livestream at least once. The Section officers, previously appointed in conformity with Division III of the Shenzhen Code, were Sandra (Sandy) Knapp (President), Nicholas (Nick) Turland (Rapporteur-général), John Wiersema (Vice-rapporteur), and Inés Álvarez and Anna Monro (Recorders). The Vice-presidents were Werner Greuter, David Mabberley, Gideon Smith, Carmen Ulloa Ulloa, and Karen Wilson. The discussions of the Section were conducted in English.

The Nomenclature Section was entitled to define its own procedural rules within the limits set by Division III of the Shenzhen Code. These procedures are detailed in the Report of Congress action mentioned in the next paragraph. Of the 433 published proposals to amend the Shenzhen Code, 134 were accepted and 22 were referred to the Editorial Committee; an additional seven were accepted from among 14 new proposals made from the floor of the Section.

The rules of the Madrid Code became effective immediately upon acceptance of the resolution, moved on behalf of the Section at the closing plenary session of the XX IBC on 27 July 2024, that the decisions and appointments of the Nomenclature Section be approved. The “Report of Congress action on nomenclature proposals”, detailing the results of the 433 published proposals and 14 floor proposals, the membership of the Permanent Nomenclature Committees (except those for fungi, see below), the establishment of four Special-purpose Committees, and the election of the Rapporteur-général for the XXI IBC (Nicholas Turland), was published on 23 September 2024 (Turland & al. in Taxon 73: 1308–1323. 2024). The full, day-to-day proceedings of the Section will be a separate publication, planned for late 2025 or 2026, following the format of previous Nomenclature Section reports (see, for example, Lindon & al. in PhytoKeys 150: 1–276. 2020 [Shenzhen]; Flann & al. in PhytoKeys 41: 1–289. 2014 [Melbourne]; Flann & al. in PhytoKeys 45: 1–341. 2015 [Vienna]).

The Nomenclature Section also elected the Editorial Committee of the Madrid Code. In accordance with Div. III Prov. 7.4, the Nominating Committee proposed members of the Section who were physically present there (with one exception) to serve on the Editorial Committee, with the Rapporteur-général and Vice-rapporteur serving as the Chair and Secretary, respectively. The Editorial Committee was increased in size from the previous 16 to the present 18 members to ensure representation from each continent, to include expertise in the main groups of organisms covered by the Code (vascular plants, bryophytes, fungi, and algae, both extant and fossil), and to improve gender balance (there are now five women on the Committee, compared with three previously).

The Editorial Committee has a mandate (Div. III Prov. 7.12) to incorporate into the new Code the changes agreed by the Section, to clarify any ambiguous wording so long as the meaning is not changed, to ensure consistency and optimal placement of provisions while retaining the present numbering as far as possible, to add, amend, or delete Examples to best illustrate the provisions, and to revise the Glossary to explain the terms used in the Code.

A first draft of the main body of the Madrid Code, incorporating the changes decided by the Section, was prepared during September 2024 by members of the Editorial Committee, as follows: Fred Barrie (Art. 7 and 10), Julia Gravendyck (Art. 8 and 9), Patrick Herendeen (Art. 11), Ronell Klopper (Art. 13–24), Sandra Knapp (Art. 60), Wolf-Henning Kusber (Art. 30–38), Anna Monro (Art. 40–49), Jefferson Prado (Glossary), Gideon Smith (Art. 61, 62, and Chapter H), Nicholas Turland (Division III), and Juan Carlos Zamora Señoret (Preamble, Rec. 5A, Art. 6 and 51–56). Chapter F was updated by the Editorial Committee for Fungi (see below). During October 2024, in response to a request made at the Section, the Glossary was thoroughly reviewed by Jefferson Prado and Michelle Price, who added new entries and amended existing entries. During October and November 2024, the first draft was updated according to edits and comments subsequently received from the members. In addition, Kanchi Gandhi compiled numerous new Examples and amendments to existing Examples. The resulting revised draft was used at the Editorial Committee meeting as the basis for discussion.

The full Editorial Committee met from 25–29 November 2024 at the Botanischer Garten und Botanisches Museum Berlin, Germany, for five days of hard work: scrutinizing the entire Code, reviewing not only the changes made in Madrid, but also reviewing the existing wording as well as potential new Examples and Glossary items referred to the Committee or suggested by Gandhi, Prado, and Price. It was an intense but highly productive week.

On 5 December 2024, a semi-final draft of the Madrid Code was completed and distributed to all Editorial Committee members for proofreading. After making final adjustments and corrections, the finished text was sent to Franz Stadler, the Production Editor of Regnum Vegetabile, on 31 December 2024 to begin the formatting and page layout. The Index of scientific names and the Subject index, compiled by Anna Monro, followed on 31 January 2025. After formatting, page layout, and final proofreading, the Madrid Code was sent to the University of Chicago Press on 3 April 2025 for publication.

Amending Chapter F – from San Juan to Maastricht

Because both the XII International Mycological Congress (IMC12), scheduled for 2022, and the XX IBC, scheduled for 2023, were delayed until 2024, the Maastricht Chapter F is published here in the Madrid Code instead of separately, as was the case for its immediate predecessor the San Juan Chapter F (May & al. in IMA Fungus 10(21). 2019).

Seven proposals to amend the San Juan Chapter F were published in IMA Fungus, the journal of the International Mycological Association (IMA), on 14 August 2024 (May & Hawksworth in IMA Fungus 15(25). 2024). A “Synopsis of proposals”, with comments by the Secretary and Deputy Secretary of the Fungal Nomenclature Session, was published on 16 August 2024 (May & Bensch in IMA Fungus 15(26). 2024). Drafts of the proposals and Synopsis, made available via the IMA website in July 2024, served as the basis for the mail vote and, together with a draft of the results of the mail vote, were made available at the Nomenclature Session.

The Nomenclature Session met on Wednesday, 15 August 2024 in Auditorium 1 of the MECC Maastricht conference centre, Maastricht, The Netherlands as part of IMC12, which took place on 11–15 August 2024. The maximum number of persons in attendance was 322, each registered for at least that day of the IMC and carrying one personal vote (there are no institutional votes at an IMC). The Session officers were Amy Rossman (Chair), Tom May (Secretary), Konstanze Bensch (Deputy Secretary), and Ewald Groenewald and Jos Houbraken (Recorders). The Deputy Chairs were Catherine Aime, Lei Cai, Pedro Crous, Irina Druzhinina, and David Hawksworth. Nicholas Turland, as Rapporteur-général elected for the XXI IBC, attended as a non-voting advisor to the Session. The discussions of the Session were conducted in English.

Of the seven published proposals to amend the San Juan Chapter F, three were accepted; an additional three were accepted from among eight new proposals made from the floor of the Session.

The rules of the Maastricht Chapter F became effective immediately upon acceptance of the resolution, moved on behalf of the Session at the closing plenary session of IMC12 on 15 August 2024, that the decisions and appointments of the Nomenclature Session be approved. The “Report of Congress action on nomenclature proposals relating to fungi”, detailing the results of the seven published proposals and eight floor proposals, the membership of the Nomenclature Committee for Fungi and Editorial Committee for Fungi, the establishment of a Special-purpose Committee, and the election of the Secretary for the Nomenclature Session of IMC13 (Tom May), was published on 21 November 2024 (May & al. in IMA Fungus 15(36). 2024). The full proceedings of the Session will form a separate publication.

The Editorial Committee for Fungi, created at the XX IBC in Madrid as a new Permanent Nomenclature Committee, consists of the following members elected at IMC12: Tom May (Chair), Konstanze Bensch (Secretary), David Hawksworth, Juan Carlos Zamora Señoret, Nicholas Turland (ex officio, Chair of Editorial Committee), and John Wiersema (ex officio, Secretary of Editorial Committee).

The Editorial Committee for Fungi prepared a first draft of the Maastricht Chapter F by incorporating the changes decided by the Session. It was sent to the Rapporteur-général, who added it to the first draft of the Madrid Code in preparation for the Editorial Committee meeting (see above). The Editorial Committee for Fungi continued to work with the Editorial Committee of the Madrid Code (the two Committees have five members in common) for the remainder of 2024.

Amendments to the Code resulting from proposals accepted in Madrid and Maastricht

Major changes

Several changes have been made to the definitions of “specimen” and “gathering” with respect to fossil-taxa. A new Art. 8.6 rules that for fossils a specimen is an individual of a fossil-species or infraspecific fossil-taxon selected from a sample of sediment or rock, which may contain multiple individuals (i.e. specimens) of the same and other fossil-taxa. Each individual (specimen) is treated as a separate gathering. Accordingly, Art. 8.2 footnote adds to the definition of “gathering” that, for most fossils, a sample is not presumed to be of a single fossil-taxon but is a set of gatherings, and Art. 8.3 footnote adds to the definition of “duplicate” that, for most fossils, there are no duplicates. A new Art. 8 Note 2 clarifies that, for the purpose of typification, both the “part” and “counterpart”, where a rock is split to reveal a fossil organ on both parts, comprise the same specimen, not separate specimens.

Finding type specimens again can be a problem with fossil-taxa, and this is addressed by the new Art. 40.8, which requires the protologue to clearly indicate the position of the holotype specimen within the rock, sediment, or preparation (for names published on or after 1 January 2026).

New Rec. 8A.5 recommends that, if a type specimen is prepared on a microscope slide, the position of that specimen on the slide should be indicated by an England Finder reference (or an equivalent) to facilitate finding it again. Rec. 8A.6 recommends that, for palaeopalynological samples, a part of the sample from which the type was selected be deposited along with the type.

Art. 9.4 on original material has been rewritten, and one important change is that illustrations are no longer original material for names of fossil-taxa. Hence if the nomenclatural type is lost or destroyed, and if there are no specimens among the remaining original material, then there is no original material and a neotype may be designated. Under the Shenzhen Code, an illustration that was original material could not be designated as a lectotype because it would be contrary to Art. 8.5, and the existence of original material precluded designation of a neotype.

Concerning priority of names of fossil-taxa (diatoms excepted) in relation to names of non-fossil taxa, two provisions in Art. 11 have been rewritten. The previous Art. 11.8 has become Art. 11.7 ruling that when the names of a non-fossil taxon and a fossil-taxon are treated as synonyms, the correct name of the non-fossil taxon must be accepted, even if it is later. The previous Art. 11.7 has been reformulated as Art. 11.8 concerning “dual nomenclature”, which accommodates “taxonomic equivalence” between a fossil-taxon and a non-fossil taxon when the names of the two taxa are not considered to be synonyms. The previous Art. 11 Note 5 on later homonyms being illegitimate whether the type is fossil or non-fossil has been moved to Art. 53 Note 3.

Art. 20.2 has been amended to end the problem of identifying generic names that coincide with Latin technical terms in use in morphology at the time of publication. Previous cases where this provision was applied are to be resolved through binding decisions, as the new Art. 20 Note 1 explains; the related Art. 20.4(b) and Rec. 20A.1(j) are also new.

Art. 40 has been thoroughly restructured, Art. 40.4 now explicitly permits the incorrect use of the term “lectotypus” or “neotypus” (or equivalents) in the protologue of the name of a new taxon to be corrected under Art. 9.10 to “holotype” to resolve the uncertain status of some names that had been treated as not validly published because the correct term “typus” or “holotypus” (or equivalents) had not been used. Art. 9 Note 9 has also been amended to accord with the new Art. 40.4. Art. 40.8 is also new and is discussed above, under names of fossil-taxa.

Art. 42 has been augmented with several new provisions (Art. 42.3, 42.5, 42.6, 42.7, Notes 1, 3, and 4, Rec. 42A.1 and 42A.2) to establish a mechanism to enable the future voluntary registration of nomenclatural novelties and type designations for algae and plants.

New Art. 51.2, together with an amendment to Art. 56.1, permits a legitimate name of a new taxon or a replacement name published on or after 1 January 2026 to be rejected if it, or its epithet, is derogatory to a group of people. In addition, the new Rec. 51A.1 advises authors to avoid publishing names of new taxa or replacement names that could be viewed as inappropriate, disagreeable, offensive, or unacceptable.

New Art. 61.6 rules that epithets with the root caf[f][e]r-, considered as highly offensive especially in Africa, are not permitted under this Code and are to be treated as orthographical variants to be replaced by epithets with the root af[e]r-. For example, the epithet ‘caffra’ is replaced by afra.

Div. III Prov. 3, concerning the allocation of institutional votes for a Nomenclature Section, has been amended so that each listed institution now has one vote, instead of one to seven votes as previously, in an effort to reduce geographical imbalance in the exercising of institutional votes. An institution applying for a vote for the first time (i.e. not on the list of institutions entitled to vote) should show that it is registered in an online, open-access international or regional index of herbaria, collections, or institutions.

Div. III Prov. 5.1 and 5.2 have been amended to put an end to almost 20 years of confusion at the Nomenclature Section when the recommendations of the General Committee are subject to a decision. A simple majority (more than 50%) of votes cast is now required to accept these recommendations. Previously, a qualified majority (at least 60%) of votes cast was required to reject them.

Div. III Prov. 7.1(c), 7.5, and 7.13 add a new Permanent Nomenclature Committee, the Editorial Committee for Fungi, responsible for preparing Chapter F of the Code, which contains the provisions solely related to names of organisms treated as fungi.

Div. III Prov. 7.10(g)(2) and 8.13(e)(2) permit Special-purpose Committees, with a specific mandate, to be appointed by the General Committee between IBCs or by the Nomenclature Committee for Fungi between IMCs for reporting back to the next IBC or IMC.

Other changes

Numerous other, smaller changes to the Code were made in Madrid. The following list is not intended to cover every change, but it discusses the more important items.

Art. 6.1 footnote, in defining “illustration”, establishes that photographs of habitat are not illustrations for the purpose of typification. Art. 9 Note 3 explains that, because such photographs are not illustrations, they cannot be original material or types.

New Art. 7 Note 4 clarifies that the effective typification of a name automatically establishes the same typification for all names sharing the same basionym or replaced synonym and for that basionym or replaced synonym. The same holds for the typification of an autonym and the name from which it is derived.

Rec. 7A.2 is new and recommends that duplicates of type material be conserved in different herbaria, collections, or institutions, preferably in different areas of the world. New Rec. 7A.3 encourages deposition of type material in herbaria, collections, or institutions in the country or countries of origin of the newly described taxon.

Art. 8.1 has been amended to clarify that the nomenclatural type of a name of a species or infraspecific taxon, which determines the application of the name (Art. 7.1 and 7.2), is a holotype, lectotype, neotype, or conserved type.

Art. 9.1 has been amended and Art. 9.2 and Note 1 are new. They provide a more precise definition of “holotype” and explain the circumstances under which a holotype can exist.

Art. 9.4 on original material now reflects a more hierarchical arrangement of elements in parallel with the order in Art. 9.1–9.7 and Art. 9.12. Clause (e) of Art. 9.4 establishes that specimens and published or unpublished illustrations (excluding illustrations of fossil-taxa, as discussed above) are original material when they were associated with the taxon by, and were available to, either the publishing author(s) or the author(s) of the validating descriptive matter.

Art. 9.24 (previously Art. 9.2) has been expanded to now allow corrections of errors made in the designation of a lectotype, neotype, or epitype. It was moved to Art. 9.24 so as to avoid renumbering the whole of Art. 9 pending a thorough review by the Special-purpose Committee on Types and Typification established in Madrid.

New Art. 10.9 provides for the automatic typification of a generic name published without species names by the type of the first name of a species assigned to that genus and validly published solely by reference to its description or diagnosis. Other cases of automatic typification are newly noted in Art. 7.3, 7.4, 7 Note 4, and 10.10.

Art. 14.14 no longer permits the proposing of changes to the places of publication of family names in App. IIB, thereby eliminating potential disruption to nomenclature and pointless editorial and committee work.

A new added clause (3) to Art. 14 Note 4(c) establishes the date of conservation of some names of fossil-taxa.

Previous guidance on the formation of generic names to avoid names not readily adaptable to the Latin language and that are difficult to pronounce in Latin has been deleted from Rec. 20A.1. A similar clause concerning specific epithets has also been deleted from Rec. 23A.3. These amendments were made with the aim of expanding the diversity of new generic names and epithets.

Art. 23.2 now limits, for names published on or after 1 January 2026, the number of characters allowed in a specific epithet, from at least two to not more than 30.

Art. 23.5 now accounts for the independent relationship between the gender of the generic name and two groups of epithets: adverbs, and nouns and their accompanying adjectives in the genitive case.

Art. 23.6 introduces a new nomenclatural act (requiring effective publication) that provides for a choice between two different grammatical categories that would be possible for certain epithets.

Art. 23.7(a) now prohibits as species names designations consisting of a generic name and an epithet in the form of a phrase in the ablative case (e.g. Solanum “fructu-tecto”).

Art. 30.4 clarifies that electronic material that has been effectively published remains as it was when effectively published even if later altered or retracted.

Adjustments to Art. 33.1 and Art. 38.14 eliminate a conflict between these two Articles for names published between 1953 and 1972, inclusive, where the requirement for a description or diagnosis had been previously fulfilled.

Art. 34 Note 1 defines works considered for suppression as being separately published books or numbered parts or supplements of a journal while Rec. 34A.2 cautions against proposing individual journal papers or series of papers for suppression, thereby discouraging proposals seeking to suppress minor works.

Art. 36.3 has been amended and redundant wording deleted so that alternative names are now defined as “two or more different names based on the same type accepted simultaneously for the same taxon by at least one author in common in the same publication”. This rule does not apply to the same combination simultaneously used at different ranks (either for infraspecific taxa or for subdivisions of a genus), and this exclusion has been extended to suprageneric names formed from the same generic name that are simultaneously used at different ranks.

New Art. 37.5 rules that statements on ranks associated with individual infraspecific names can be used to assign rank throughout a whole publication provided that they do not result in misplaced terms contrary to Art. 5 and when no general statement on the different infraspecific ranks used in that publication is made.

New Art. 38.4 provides the definition of “description” that the Code previously lacked. Because it also rules that a description need not be diagnostic, Art. 38 Note 2 in the Shenzhen Code became redundant and has been deleted.

Art. 41 Note 2 provides guidance on how to cite page numbers from publications that lack them. This new Note suggests four options while pointing out that a DOI or URL is not by itself sufficient to indicate a page. Rec. 41A.2 has been amended to recommend enclosing page numbers (or an indication of their absence, e.g. “without page number”) in square brackets when they are cited according to Art. 41 Note 2.

A new opening sentence in Art. 48.1 contrasts a misapplication of an existing name, when the type has not been excluded, with creation of a later homonym, when the type has been excluded. Further clarification on what constitutes exclusion or inclusion of the type of a name appears in Art. 48.2, with exclusion of the name itself now also to be considered. New Art. 48 Note 3 indicates that inclusion of an apparent basionym with an expression of doubt, or only in part, does not by itself constitute exclusion of its type.

Two new Notes address the implications of nothogeneric names not having types (see Art. H.9 Note 1). Art. 52 Note 5 explains that nothogeneric names, because they have no types, do not cause nomenclatural superfluity and Art. 53 Note 2 points out that nothogeneric names, even though they have no types, can be homonyms (of each other or of non-hybrid generic names).

Art. 38.5 and Art. 53.4 now rule that binding decisions on valid publication and homonymy, respectively, take retroactive effect upon publication of the General Committee’s report containing the decisions, but this is subject to ratification by a later IBC. This now permits binding decisions to be added to App. VI and VII between IBCs, thereby streamlining the decision-making process.

An addition to the final clause of Art. 60.8 precludes changes to terminations that conform to classical Latin adjectival usage other than that dealt with by Rec. 60C.1, e.g. Cephalotaxus harringtonia (Knight ex J. Forbes) K. Koch is not to be changed to C. ‘harringtonii’.

New Art. 60 Note 3 clarifies that epithets derived from personal names with a well-established latinized form may be formed according to either Rec 60C.1 or Art. 60.8, hence martini and martinii both commemorating Martin, which has the well-established latinized form Martinus, are both correct and are not to be changed.

New Art. 60.9 rules that an epithet (or final portion thereof) formed from abbreviation of one or more personal names is considered to have been composed arbitrarily (which is permitted by Art. 23.2) and is not to be changed, e.g. under Art. 60.8.

Art. 60.12 has been amended to hopefully provide more clarity on the use or non-use of hyphens in epithets, i.e. when must a hyphen (present at valid publication) be deleted and when may a hyphen be added after valid publication. A set of four conditions, (a) (1 and 2) and (b) (1 and 2), is provided, and a hyphen is permitted only when at least one condition of (a) and at least one condition of (b) are met. However, this still does not result in a single outcome in every case. When, for example, a name is published with an epithet consisting of two words separated by a space, Art. 60.12 permits a hyphen to be inserted (replacing the space), while Art. 23.1 requires either uniting the two words (by deleting the space) or inserting a hyphen (replacing the space). On the other hand, when a name is published with an epithet containing neither a hyphen nor a space, a hyphen may not be inserted.

Art. F.2.1 and F.7.1 have been revised to more clearly set out the steps involved in the procedures for lists of protected and/or rejected names of organisms treated as fungi. Art. F.2 Note 1 makes it clear that, when preparing lists of names for protection, included names may be proposed with or without the listing of synonyms, because Art. F.2.1 rules that protected names are treated as conserved against any competing synonyms.

New Art. F.3.5 rules that an earlier homonym of a sanctioned name remains unavailable if the sanctioned name is rejected under Art. 56 or F.7.

An addition was made to Art. F.5 Note 3 to clarify that an identifier is not required when proposing a conserved type of a name of an organism treated as a fungus.

Two new Recommendations concerning types that are living cultures of organisms treated as fungi were added at the end of Chapter F. Rec. F.11A.1 augments Rec. 8B.1 by recommending that when ex-type cultures are deposited in institutional culture or genetic resource collections, those collections should be public. Rec. F.11A.2 recommends utilizing the oldest progeny of an ex-type culture when it is permitted to designate a neotype to replace a nomenclatural type that has been lost or destroyed.

Art. H.5.2 has been amended with respect to naming a nothotaxon with parent taxa at unequal ranks (species and infraspecific taxa). The appropriate rank of the nothotaxon is the lowest of these ranks, unless the nothotaxon is the only one known for hybrids between the species to which the parental taxa of the nothotaxon belong.

A new Div. III Prov. 4 Rec. 2 recommends that individuals or groups should be able to observe the Nomenclature Section of an IBC online and that the Organizing Committee of the IBC in consultation with the Bureau of Nomenclature should be responsible for implementing this. Exactly this happened at the XX IBC in Madrid in July 2024.

Editorial amendments to the Code

Several improvements have been made to the organization and presentation of the Code’s provisions. In addition to the usual titles of Divisions, Chapters, and Sections, the Madrid Code now includes titles of individual Articles. These titles were inspired by those used in the online version of the Shenzhen Code, with adjustments to make them more self-contained, and were the joint effort of Julia Gravendyck and Werner Greuter. They are now also mirrored in an expanded Contents, allowing users to more easily find what they want.

For Articles that group multiple items together, often as conditions with any one or all required, the items have been organized into lettered and sometimes numbered clauses, as was already done for some provisions in the Shenzhen Code. This format makes the Articles more digestible and facilitates citation of individual clauses. When an Example is relevant to a particular lettered clause, the respective letter is cited in parentheses, usually at the beginning of the Example, e.g. “(c)” in Art. 9 Ex. 19. Numbered clauses are sometimes also cited, and a condensed format, e.g. “(a1, b2)”, is used to avoid repetitive parentheses in Art. 60 Ex. 48–51.

Translations of words, phrases, and quotations in languages other than English (e.g. Chinese, Dutch, French, German, Latin, Russian, or Spanish) have now been provided wherever these appear, thanks to the efforts of Tom May with Latin advice from Werner Greuter.

In Division III, the Editorial Committee noticed that Prov. 7.10, which claimed to list the functions of the General Committee, did not in fact provide a comprehensive list, omitting several functions mentioned in Art. 42 and elsewhere in Div. III. Therefore, Prov. 7.10 has been expanded to enumerate all the functions of the General Committee compiled editorially from content already in the Code. Mirroring Prov. 7.10, a new Prov. 8.13 has been added to enumerate all the functions of the Nomenclature Committee for Fungi compiled editorially from content already in Chapter F and Div. III. A small, editorial addition to Prov. 7.15 comes from Art. 42.2 specifying that the Registration Committee considers applications for recognition as nomenclatural repositories for organisms other than those treated as fungi.

The Editorial Committee of the Shenzhen Code added bibliographic references to the Examples, as explained in the Preface of the Shenzhen Code (p. xxii). Over the last seven years, a number of errors have been discovered, in particular by Paul van Rijckevorsel, and these have been corrected. Where the same reference (same author(s) and publication) appears more than once within an Example, the abbreviation “l.c.” (loco citato, in the place cited) is used to avoid undue repetition.

Throughout the Madrid Code, the abbreviation “nom. sanct.” (nomen sanctionatum) has been added wherever sanctioned names of organisms treated as fungi have been cited (replacing the previous convention of citing author : sanctioning author).

A number of linguistic improvements have been implemented as well, such as using more modern and plain English where the meaning is not changed and avoiding ambiguous words, e.g. altering: “bear” to “have”; “collection” to “specimen” or “gathering” or “material collected” (unless a herbarium, collection, or institution is meant); “common” to “frequent” (unless used in the sense of shared, e.g. “in common”); “commonly” to “often”; “despite the fact that” to “even though”; “effected” to “achieved” (where appropriate, as requested by the Section in Madrid); “failed to” to “did not”; “in order to” to “to” (where appropriate); “ineffective” to “not effective”; “irrespective” to “regardless”; “location” to “locality” (where geographical) or “position” (e.g. on a microscope slide); “male” and “female” to “staminate” and “pistillate” (where describing angiosperms, not people or hybrid parents); “name of a person” to “personal name”; “notwithstanding” to “despite”; “ought to” to “should” (where appropriate); “parent” to “parental” (where used as an adjective); “prior” to “earlier” (where used as an adjective); and “prior to” to “before” (where appropriate). The phrases “for the purpose of” and “for the purposes of” were reviewed for the appropriate usage of singular or plural. A few words or phrases have been deleted, such as “pleonasm” (Rec. 23A.3(e)) and “bona fide” (Rec. 7A.1), although “infringements” (Art. H.10.1) remain for someone to propose a change at a future IBC.

Latin terms and their abbreviations used in the Code

A number of Latin terms and/or their abbreviations appear throughout the Code that may not be readily understood, especially by first-time users, so these have been compiled, in particular by Tom May and Werner Greuter, into a separate listing as part of the front matter. Terms are listed alphabetically together with the abbreviations, if they exist, and their meaning is provided in English.

The Glossary

The Glossary has retained its basic structure but has been revised and updated, as mentioned above, by Jefferson Prado and Michelle Price. New entries in the Glossary are as follows: “adopted name”, “circumscription”, “conserved type”, “dual nomenclature”, “nomenclatural repository”, “original author(s)”, “original type”, “personal name”, “phrase name”, “registration”, “taxonomic equivalence”, “type citation”, “type indication”, and “typify”. Some existing entries have been substantially revised, e.g. “automatic typification”, “description”, “epitype”, “gathering”, “identifier”, “isosyntype”, “isotype”, and “nomenclatural type”. The entry for “binary combination” has been changed to “binomial” to accord with the preferred term in the Code. The entry for “unispecific” has been deleted because it was used only in Art. 36 Ex. 1, where “unispecific genus” was rephrased as “genus of one species”. This reflects the fundamental role of the Glossary, which is strictly to explain terms used in the Code, and where possible to do so using the precise wording associated with these terms in the Code. The Glossary does not seek to cover all terms useful in the nomenclature of algae, fungi, and plants; for that, users can refer to a work such as Hawksworth, Terms used in Bionomenclature (2010; online at https://www.gbif.org/document/80577).

The Appendices

The Appendices of the Code have been maintained over the last several years by John Wiersema as an online database currently hosted by the Department of Botany at the Smithsonian National Museum of Natural History in Washington, DC (https://naturalhistory.si.edu/research/botany/codes-proposals). The Appendices will continue to be available online in this form, while the possibility of publication as printed matter or in Portable Document Format (PDF) is not precluded. The online database not only generates any or all of the Appendices of the Code, but it also provides an accounting of all proposals to conserve, protect, and reject names, to suppress works, and all requests for binding decisions since the first proposals appeared in 1892. The database can be searched using various criteria, and the matching content is reported in two different ways. A “Code Appendices” report reproduces all entries matching any set of search criteria within Madrid Code Appendices I–VII. A “Proposals/Requests” report details the history of selected proposals or requests, providing citations of all Nomenclature Committee reports regarding their status, and indicating the final determination, the presence, if any, in earlier Code Appendices, and any resulting entries in the Madrid Code Appendices.

In support of Art. 14.15, 34.2, 38.5, 53.4, 56.3, F.2.1, and F.7.1, which rule that once proposals or requests have been approved by the General Committee their effects become authorized, any names or works involved in such proposals or requests can be promptly added to the online Appendices, eliminating unnecessary publication delays. Nearly 800 new Appendix entries have thus been generated since the 2018 Shenzhen Code, initially preceded by an asterisk (*), but with ratification by the Madrid IBC the asterisks have been deleted.

Lists of protected names of fungi (Art. F.2.1) approved for both the Shenzhen and Madrid Codes, and incorporated according to their rank in App. IIA, III, and IV, were initially protected only against listed synonyms. Because they are now protected against unlisted synonyms as well, there is no longer a need to list synonyms for protected names, so the Editorial Committee has decided to remove them. No lists of rejected names of fungi (Art. F.7.1) have yet been approved.

Formatting and standards used in the Code

Recent editions of the Code have used three different sizes of type, with the Recommendations and Notes set in smaller type than the Articles, and the Examples and footnotes in smaller type than the Recommendations and Notes. These type sizes, which have been maintained in this edition, reflect the distinctions between mandatory rules (Articles), complementary information (Notes) or non-mandatory advice (Recommendations), and explanatory material (Examples). Notes, unlike Articles, do not introduce any new provision or concept; rather they explain something that may not at first be readily apparent but is covered explicitly or implicitly elsewhere in the Code. Consequently, if an apparent conflict is perceived between a Note and an Article, the Article should be followed. Notes are appropriately identified (at least in the print edition of the Code) with an “i” for “information”, highlighted in the same way as the Article numbers. Examples are distinguished, in addition to the smaller font size, by being indented. An Example prefixed by an asterisk (*) is a voted Example, which is comparable to a rule (see Art. 7 *Ex. 17 footnote). Footnotes provide supplementary material to the Preamble, Articles and Examples in Div. II, and Provisions in Div. III.

As in all recent editions, scientific names under the jurisdiction of the Code, irrespective of rank, are consistently given in italic type. The Code sets no binding standard in this respect, because typography is a matter of editorial style and tradition, not of nomenclature. Nevertheless, in the interest of international uniformity, editors and authors could consider following the practice exemplified by the Code, which has been well received in general, is followed in a number of botanical and mycological journals, and was emphatically recommended by Thines & al. (in IMA Fungus 11(25). 2020). To set off scientific names even better, italics are not used for technical terms and other words in Latin, although they are still used for word elements that are part of a scientific name and for non-abbreviated titles of books or journals.

Double quotation marks are used to denote designations, to readily distinguish them from validly published names, e.g. “Echinocereus sanpedroensis”. Single quotation marks are used to denote incorrect spellings of validly published names, e.g. Gluta ‘benghas’ L. Double quotation marks are also used to indicate text that is quoted verbatim, with single quotation marks enclosing quotes within quotes.

The Editorial Committee has tried hard to achieve uniformity in bibliographic style and formal presentation. Author citations of scientific names appearing in the Code are standardized in conformity with Brummitt & Powell, Authors of plant names (1992), updated as necessary from the International Plant Names Index (IPNI; https://www.ipni.org/), albeit with additional spacing, as mentioned in Rec. 46A Note 1. The Code has placed a space after a full stop (period) in author citations since the 1906 Vienna Rules (Briquet, Règles Int. Nomencl. Bot. 1906), whereas Authors of plant names recommended against placing spaces after full stops and has been followed by IPNI. The use or non-use of spaces in standard author citations is a matter of editorial style, and neither method is incorrect. The titles of books in bibliographic citations are abbreviated in conformity with Taxonomic literature, ed. 2 (TL-2; Stafleu & Cowan in Regnum Veg. 94, 98, 105, 110, 112, 115, 116. 1976–1988; Supplements 1–6 by Stafleu & Mennega in Regnum Veg. 125, 130, 132, 134, 135, 137. 1992–2000; Supplements 7 and 8 by Dorr & Nicolson in Regnum Veg. 149, 150. 2008, 2009; online at https://www.sil.si.edu/DigitalCollections/tl-2/index.cfm) or, when not in TL-2, by analogy, but always with capital initial letters. For journal titles, the abbreviations follow BPH Online (Botanico-Periodicum-Huntianum; https://huntbot.org/bph/) or, when not in BPH Online, by analogy. Standard herbarium codes follow Thiers, Index Herbariorum (continuously updated; online at https://sweetgum.nybg.org/science/ih/).