International Code of Botanical Nomenclature

(Saint Louis Code), Electronic version



The rules that govern scientific naming in botany (including phycology and mycology) are revised at Nomenclature Section meetings at successive International Botanical Congresses. The present edition of the International code of botanical nomenclature embodies the decisions of the XVI International Botanical Congress held in St Louis in 1999 and supersedes the Tokyo Code, published six years ago subsequent to the XV International Botanical Congress in Yokohama. It is written entirely in (British) English. The Tokyo Code has been translated into Chinese, French, German, Italian, Japanese, Russian, and Slovak; it is therefore anticipated that the St Louis Code, too, will become available in several languages in due course.

The St Louis Code does not differ substantially in overall presentation and arrangement from the Tokyo Code, and the numbering of Articles and Appendices remains the same, although there have been a few changes in the numbering of paragraphs, Recommendations and Examples. In the Tokyo Code extensive renumbering had taken place, and therefore its preface included a tabulation comparing the placement of its provisions with those of the preceding (Berlin) edition. This time, no such tabulation is included.

The text of the Code uses three different sizes of print, the Recommendations and Notes being set in smaller type than the Articles, and the Examples and footnotes in smaller type than the Recommendations and Notes. The type sizes reflect the distinction between the rules which are mandatory (Articles), complementary information or advice (Notes and Recommendations), and explanatory material (Examples and Footnotes). A Note has binding effect but does not introduce any new provision or concept, rather, it explains something that may not at first be readily apparent but is covered explicitly or implicitly elsewhere in the Code. Some Examples, which were deliberately agreed by a Nomenclature Section, contain material which is not fully, or not explicitly, covered in the rules. Such "voted examples" are prefixed by an asterisk (*). If, by a change of the corresponding provision in a subsequent edition of the Code, a "voted example" becomes fully covered, the asterisk is removed.

As in the previous edition, scientific names under the jurisdiction of the Code, irrespective of rank, are consistently printed in italic type. The Code sets no binding standard in this respect, as typography is a matter of editorial style and tradition not of nomenclature. Nevertheless, editors and authors, in the interest of international uniformity, may wish to consider adhering to the practice exemplified by the Code, which has been well received in general and is being followed in an increasing number of botanical and mycological journals. To set off scientific plant names even better, the use in the Code of italics for technical terms and other words in Latin, traditional but inconsistent in past editions, has now been abandoned.

As its forerunners, the Editorial Committee has tried hard to achieve uniformity in bibliographic style and formal presentation - a sound educational exercise for its members, and a worthwhile goal because the Code is considered a model to follow by many of its users. The titles of books in bibliographic citations are abbreviated in conformity with Taxonomic literature, ed. 2, by Stafleu & Cowan (1976-1988; with supplements by Stafleu & Mennega, 1999-2000), or by analogy. For journal titles, the abbreviation follows the Botanico-periodicum-huntianum (1968) and its supplement (1991).

Author citations of scientific names appearing in the Code are standardized in conformity with Authors of plant names, by Brummitt & Powell (1992), as mentioned in Rec. 46A Note 1. One may note that the Code has no tradition of recording the ascription of names to pre-1753 authors by the validating author, although such "pre-ex" author citations are permitted (see Art. 46 Ex. 21). Previous editions of the Code had no uniform policy with respect to parenthetical author citations for suprageneric names, as the provisions themselves provide no concrete guidance on the matter. For consistency, the Editorial Committee has now opted for omission of parenthetical authors at the higher ranks throughout the Code, but by this policy it does not intend to prejudge the conclusions of the Special Committee on Suprageneric Names, set up in St Louis.

The St Louis Congress was conservative in nomenclatural matters in comparison to its predecessors. Few substantive changes were allowed, but many useful clarifications and improvements of the Code, both of wording and substance, were accepted. Here we only draw attention to changes of some note. An exhaustive report on the Section's decisions has been published elsewhere (Barrie & Greuter in Taxon 48: 771-784. 1999).

The single largest area of change in the St Louis Code concerns typification, where many excellent proposals had been submitted by the Special Committee on Lectotypification. In Art. 8.2, the definition of a type specimen was revised, to make it clear that multiple plants or plant fragments belonging to one and the same gathering and taxon, when mounted together on a single herbarium sheet or in an equivalent preparation, form one specimen. Designations of only part of such specimens as lectotypes are thus inappropriate in the future, and those of the past become irrelevant. Under certain conditions, a specimen may even comprise more than one sheet or preparation (Art. 8.3). For the purpose of valid publication, indication of the type may, under the novel Art. 37.2, refer (explicitly or by implication) to more than one specimen, provided that all are duplicates belonging to a single gathering. Because in such a case the type material consists of more than one specimen there is no holotype, so a lectotype may be chosen from among the specimens. The same procedure is now outlined in Art. 9.14 for the analogous situation of an alleged lectotype or neotype that is found to comprise two or more duplicate specimens. The new provisions of Art. 9.18-9.19 clarify the status of epitypes and the requirements for their designation, thus greatly improving the usefulness of the epitype concept which had been introduced six years before by the Tokyo Congress. Finally, the controversial, Janus-faced former Art. 8.3, specifying when illustrations may serve as types, was amended so that it can no longer be perceived to constrain the freedom of lectotype designation; in its new position, as Art. 37.4, it is a clear and straightforward impediment to the valid publication of post-1957 names of species or lower-ranking taxa that are based on type illustrations.

The second major change decided at St Louis was not based on a published proposal but on a motion from the floor, which was carried after an emotional, truncated debate: that all reference to registration of new botanical names, to become mandatory from a future date, be deleted from the Code, where they had been introduced by the Tokyo Congress six years before - indeed a surprising reversal of opinion between two subsequent Congresses.

Other new matter to be found in the present edition of the Code is of comparatively lesser importance, as it either is of a non-mandatory, explanatory or advisory nature; or does not concern all botanical organisms but only specified groups such as fossils, algae, or fungi; or consists in reorganising and clarifying some previously unclear or contradictory provisions; or takes effect only from a date in the future.

Three new non-retroactive rules were introduced at St Louis, all concerning typification. The Editorial Committee has power to fix the date from which such provisions take effect. It opted for the turn of the millennium: 1 January 2001. This is one year earlier, relatively speaking, than for previous editions; the main reason being that the time needed for publishing the St Louis Code (9 months) was significantly shorter than for earlier editions (1 to 3 years). Two of the non-retroactive provisions concern the conditions that new type designations must meet to be effective (Art. 7.11: use of the phrase "here designated", or equivalent wording; Art. 9.21: use of the term "lectotypus" or "neotypus", or their equivalent). The third (Art. 38.2, also referred to in Art. 9.13) applies only to the names of new taxa of fossil plants and requires, as a condition for valid publication, that one accompanying illustration be explicitly stated to represent the type.

One further date limit first appears in the St Louis Code. From 1 January 1908 onward, the terminations of suprageneric names are accepted as defining their rank, in the absence of an explicit rank-denoting term (Art. 35.2). The now familiar rank-specific standard terminations had been introduced in 1905 by the first Vienna Congress, which explains the choice of date. The Section had to consider many other proposals aimed at reforming suprageneric nomenclature, most of which it defeated and referred to an apposite Special Committee for further study. It did, however, agree to clarify, simplify and restructure the rules governing suprafamilial names (Art. 16-17), without changing their meaning.

Article 33, dealing with new combinations, is another portion of the Code that the Section agreed to improve. One problem that had long been known was that names obviously intended as new combinations but lacking an explicit reference to their would-be basionym did sometimes fulfil the requirements for valid publication as names of new taxa, with consequent loss of priority, change of type, and other potentially negative side-effects. This has now been remedied by new Art. 33.2. Another source of trouble was the apparent conflict between former Art. 33.3 (errors of bibliographic citation are permissible) and 33.4 (citation of the wrong source is not permissible), relevant in the case of combinations published after 1952. This conflict has now been resolved: Art. 33.4 defines citation errors in a restrictive way, Art. 33.5 reaffirms that citation of the wrong source is not a correctable error, and Art. 33.6 specifies some useful exceptions to the latter rule.

Article 58 was completely rewritten and substantially shortened, but its meaning (in so far as it had one) was not thereby affected. - Upon a motion from the floor, -glochin was defined to be feminine when terminating a compound generic names, while -phykos will have to be treated as masculine although it was neuter in classical times (Art. 62.2(b-c)). - A change in Art. 21.2 clarified the status of names of subdivisions of genera that were given a genitive noun as their epithet. It is now explicit that genitive nouns are acceptable as such epithets only in the plural, not in the singular. This provision is relevant mainly if one wishes to derive the epithet in the name of a subdivision of a genus from the name of an included species, when one may not adopt unchanged substantival epithets in the genitive singular (such as "Linnaei"), but may instead transform them into plural adjectives (e.g., Linnaeani).

Fossil plant nomenclature underwent profound changes at St Louis. It is hardly exaggerated to say that the accepted compromise solution, that an ad hoc group of specialists worked out while the Section met, provides for the first time ever a sound, workable formal basis for past and current practice in palaeobotanical nomenclature. For nomenclatural purposes, botanical fossils are now considered to belong in the first place to morphotaxa: taxa at definite ranks that comprise only particular parts, life stages, or preservational states but not the whole organism (Art. 1.2). Formal synonymy, and the operation of the priority principle, are confined within the framework and boundaries of morphotaxa (Art. 11.7). The qualitative definition of morphotaxon categories is not regulated by the Code but is wisely left for the practising palaeotaxonomist to decide. Similarly, the recognition and naming of "biological" fossil taxa, in the sense of evolutionary units consisting of whole organisms, is not dealt with in the Code, which gives full latitude to those interested in such basically hypothetical concepts to use for them the names that are best suited for the purpose. Let us explain: Sigillaria, nomenclaturaly speaking, is the name of a morphogenus comprising certain bark fragments, as the ultimate type of the generic name (the type specimen of S. scutellata) is such a bark fragment; yet when referring to Carboniferous forests in which trees with Sigillaria bark predominated, it is permissible and makes perfectly good sense to speak of Sigillaria forests. Sigillariaceae nomenclaturally designates a bark fragment morphofamily, but may be used for a hypothetical evolutionary family which, among others, includes members of the cone genus Mazocarpon (see Art. 11 Ex. 25).

As strict synonymy and therefore priority only operates among morphotaxa of the same kind, names of botanical fossils cannot logically compete with names based on a non-fossil type. By consequence, the former Art. 11.7, which ruled that names of non-algal non-fossil taxa take priority over names of fossils, has been downgraded to the status of a Note (Art. 11 Note 4). Moreover, the former algal exception was restricted to diatoms (Bacillariophyceae) alone, since they are the only algal group for which a different treatment is important and useful. Nomenclaturally speaking, fossil algae other than diatoms are now assimilated to fossil plants, being assigned to morphotaxa, whereas no difference is made between fossil and non-fossil diatoms. This statement is true in the context of synonymy and priority but not of valid publication, as for the latter purpose fossil diatoms, as previously, count with the fossils not with the algae (see Art. 36.2-3, 38-39). Specialists should be alert to this apparent anomaly in the Code and to the potential difficulties it may cause, so that a change, if worthwhile, can be envisaged in the future.

There are some minor changes regarding typification provisions that are relevant to fossil plant nomenclature alone. They concern Art. 38.2 (already mentioned) and 9.13.

Fungal nomenclature was only affected in a marginal way by decisions of the St Louis Congress. Some editorial improvements of the special rules on fungal anamorphs are worth mentioning (see Art. 59.4 in particular), as well as a new recommendation (59A.3) that discourages the creation of anamorph names that are not really needed. The former "mandatory recommendation" 60H was promoted to Article status (60.12) and had its coverage extended from "host plants" to all "associated organisms" after which a fungus is named. Rec. 50E.2, addressing the way in which the sanctioned status of a fungal name is indicated in its author citation, has been made more explicit and of more general application. Finally, the former "voted example" by which it was ruled that cultures preserved in a metabolically inactive state are acceptable as types (Art. 8 Ex. 1) has, most appropriately, received an explicit legal basis in Art. 8.4, where it is also spelled out that this option exists for algae and fungi alike.

Among the non-mandatory (explanatory or advisory) matter added or modified at St Louis, let us point out the reworded Art. 46.1, which downgrades author citation after scientific names, from a necessary condition for a name to be "accurate and complete" to a mere complement that "may be desirable", particularly in taxonomic and nomenclatural publications. Authors and editors should be made aware of this change, as past editorial policy has sometimes enforced the uncritical addition of author citations in non-taxonomic papers, where they are of little use. - One new term, "isonym", has been introduced into the Code (Art. 6 Note 1), defined to mean the same name used independently by different authors at different times - a nomenclaturally irrelevant notion that may perhaps be useful occasionally for the sake of an argument.

Among the portions of the Code that remain virtually unchanged after St Louis, are the two for which by far the largest number of amendment proposals had been submitted: orthography and the naming of hybrids. For the latter domain, the proposer himself suggested that implementation of the proposed changes was premature, and that a special "inter-Code Committee" should be asked to consider how best to coordinate the provisions on hybrids in the botanical Code and in the Intenational code of nomenclature for cultivated plants. The Section gladly agreed; but as to orthography, it not only turned down in disgust the countless and partly conflicting proposals that had been made, but also refused to set up a new committee to consider the numerous still unresolved issues.

A series of loosely related proposals had the aim of promoting harmony and co-ordination between the different sets of rules governing botanical, zoological, bacterial and viral nomenclature. The Section was only marginally more lenient with respect to these proposals than with the orthographical ones. Yet, some progress was achieved. In the field of terminology, the terms "homotypic synonym", "heterotypic synonym" and "replacement name" were accepted as optional equivalents of the earlier "nomenclatural synonym", "taxonomic synonym", and "avowed substitute". The terminations -viridae, -virales, -virinae, and -virus were outlawed for names of subclasses, orders, subtribes, and genera, respectively (Rec. 16A.3(c), Art. 17.1, 19.3, and 20.1), so as to avoid possible future homonymy or confusion with names of viruses. A new recommendation (54A) endeavours to dissuade authors naming new botanical taxa from using names that already exist in zoology or bacteriology. The Section also encouraged ongoing efforts toward inter-Code harmonization by approving the set-up of a Special Liaison Committee.

The St Louis Code was prepared according to the procedures outlined in Div. III, which have been operating with hardly any change since the Paris Congress of 1954. 215 individual numbered amendment proposals were published in Taxon between February 1996 and November 1998. Their synopsis, with comments by the Rapporteurs, appeared in Taxon (48: 69-128) in February 1999 and served as the basis for the preliminary, non-binding mail vote by the members of the International Association for Plant Taxonomy (and some other persons), as specified in Division III of the Code. Tabulation of the mail vote was taken care of by the Nomenclature Section's Recorder, F. R. Barrie. The results were made available to the members of the Nomenclature Section at the beginning of its meetings; they were also tabulated in the November 1999 issue of Taxon (48: 777-782), along with the action taken by Congress.

The Nomenclature Section met at the Missouri Botanical Garden, St Louis, Missouri, U.S.A., on 26-30 July 1999. The St Louis Section was the best attended of any Congress so far. It had 297 registered members carrying 494 institutional votes in addition to their personal votes. The Section Officers, previously appointed in conformitiy with Division III of the Code, were H. M. Burdet (President), F. R. Barrie (Recorder), W. Greuter (Rapporteur-général), and D. L. Hawksworth (Vice-Rapporteur). Each Nomenclature Section is entitled to define its own procedural rules within the limits set by the Code, but tradition is held sacred. As on previous occasions, a 60 % assenting majority was required for any proposed change to the Code to be adopted. Proposals rejected by 75 % or more in the mail ballot were ruled to be defeated unless raised anew from the floor. The proceedings of the nomenclature sessions are presently being edited, based on a tape transcript. They will be published later this year in the serial Englera.

The Nomenclature Section also appointed the Editorial Committee for the St Louis Code. As is traditional, only persons present at the Section meetings were invited to serve on that Committee, which as the Code requires is chaired by the previous Rapporteur-général and as is logical includes the Vice-Rapporteur as its secretary and the new Rapporteur, who will serve at the next (Vienna) Congress, as vice-chairman. The Editorial Committee, complete as elected, convened on 23 January 2000 at the Botanischer Garten und Botanischer Museum Berlin-Dahlem, Berlin, Germany, for a full week's hard work. The Committee worked on the basis of a draft of the text of the main body of the Code, prepared by the Chairman to incorporate the changes decided by the Section, which was distributed by electronic mail on 25 November 1999; and of a preliminary version of the proceedings of the Section meetings, e-mailed between 25 November 1999 and 1 January 2000 as transcribed from tape and revised portion-wise by F. R. Barrie, D. L. Hawksworth, and J. McNeill.

Each Editorial Committee has the task of addressing matters specifically referred to it, incorporating changes agreed by the Section, clarifying any ambiguous wording, ensuring consistency, and providing additional examples for inclusion. The terms of the Committee's mandate, as defined by the Section in St Louis at its constituent meeting, included the usual empowerment to alter the wording, the examples, or the location of Articles and Recommendations, in so far as the meaning was not affected; while retaining the present numbering in so far as possible.

The full Editorial Committee concentrated on the main body of the Code, including Appendix I (hybrids) and the texts heading Appendices II-V. A new electronic draft of these portions was completed immediately after the meeting, which was proof-read by all Committee members. The contents of Appendices II-V were revised and updated in a bilateral process involving the Chairman and a specialist for each of the groups concerned, normally a Committee member (V. Demoulin for the fungi, D. H. Nicolson for vascular plants, P. C. Silva for the algae, J. E. Skog for fossil plants), except for the bryophytes (G. Zijlstra, Utrecht, with assistance from P. Isoviita, Helsinki). The Subject index and the appended Index to scientific names were prepared entirely by P. Trehane; the remodelled Index to the Appendices was compiled by W. Greuter, who also cared for the final copy-editing, formatting, and the production of camera-ready copy.

Two of the Appendices call for special comments. The Section on a straw vote had indicated preference for an alphabetical sequence of entries of all conserved generic names, within the major groups. Alphabetizing, for spermatophyte genera, was tantamount to abandoning the former numerical classification of the venerable but obsolete Dalla Torre & Harms system. In the electronic age this operation, which might once have been a nightmare, proved to be fairly easy, so the Editorial Committee was pleased to comply with the Section's wish. It was less pleased with the Section's ill-advised instruction (not alas a mere wish) to revise the list of conserved spermatophyte family names, abandoning the (informally introduced but not regularly approved) 1789 starting-point date of the previous list and introducing numerous other changes of authorship and date, the need for which had been brought to light by the bibliographic searches of J. E. Reveal. This task, which F. R. Barrie and N. J. Turland had volunteered to undertake jointly, proved to be quite demanding and indeed in part impossible to achieve, because Reveal's list of suggested changes was found to be less dependable than he (and the Section) had anticipated. Barrie and Turland, who managed to verify all relevant entries to the original source, had to conclude that in many cases a change was unwarranted, and in other cases it should better wait until the conclusions of the Special Committee on Suprageneric Names were known. The following explanatory notes, by Turland, will illustrate the problems encountered and the solutions adopted.

"We have accepted only those names which we are confident are validly published at the rank of family. We have notes on all the dubiously correct and obviously wrong authors and references on Reveal's list, and will make these available to the Special Committee [on Suprageneric Names. In particular,] we removed the Berchtold & J. Presl names because they probably have to be taken as orders ('rad'), with some of them subdivided into families ('celed'). According to [the consulted Czech and Slovak botanists] K. Marhold, J. Kirschner, and J. Stepanek, while 'rad' means order, 'celed' can only mean family, both now and in 1820. On advice from H. M. Burdet, we regard the names in Durande (1782) as not validly published because they are not accepted by the author, but rather are merely an account of Jussieu's system. The names of Batsch (1796) are dubious: while a few seem acceptable, many others are groups with descriptive names such as Drupiferae, Pomiferae, Senticosae, Multisiliquae, Succulentae, Arillatae, Pentacarpae, Rostratae, Ciliatae, Hesperideae, Sarmentaceae, Fimbriatae, etc. Moreover, 'Piperitae' (accepted by Reveal as Piperaceae) appear to have nothing to do with Piper but are instead based on Arum. It seems better to leave all these names out. Several other, individual names have also been excluded. We are preparing a paper for Taxon explaining what we have done."

Fortunately, after Barrie's and Turland's critical review, the only pre-Jussieu (pre-1789) entries that had to be accepted are those from Adanson (1763) which at least is a well-known work, many familiar names being involved. Still, we want to discourage users from introducing changes of family names that appear to result from acceptance of the new list but would go against the previous one. The Section was given the promise that such changes would be avoided by timely conservation action, and although not even the relevant proposals have yet been published, it is reasonable to assume that such action will eventually be taken. Therefore, e.g., the family including both Vaccinium L. and Erica L. should better remain known as Ericaceae Juss. and not renamed Vacciniaceae Adans. (an example which, incidentally, is not among those that were mentioned before the Section).

This is the proper place for us to thank all those who have contributed to the publication of the new Code: our fellow members of the Editorial Committee for their forbearance, helpfulness, and congeniality; all the persons, just named, who contributed in a special way and much beyond their normal commitment to particular editorial tasks; the botanists at large who volunteered advice and suggestions, including relevant new examples; Mrs R. Ziegler for speedily typing the raw transcript of the nomenclature sessions' tape recordings; the International Association for Plant Taxonomy and its new Secretary, Tod Stuessy, for having honoured IAPT's traditional commitment to plant nomenclature by funding the Editorial Committee meeting in Berlin; and the publisher, Sven Koeltz, for his helpfulness and the speed with which he once again showed the Code through the print. As our nomenclatural mandate now comes to an end, this is also the proper time and place for a general if personal epilogue. 

Biological nomenclature is the means of channelling the outputs of systematic research for general consumption. It is not only the taxonomists' concern but is of relevance for all who need to communicate about organisms. Nomenclature Sections at preceding Congresses had been increasingly aware of this fact and of the consequent need to make organismal nomenclature and the rules governing it subservient to the needs of the world at large. During the period in which we have been associated with the development of the Code, major changes have been implemented which promote the stability of names and their application, including conservation of species names, rejection of names at any rank, introduction of the epitype concept, and acceptance of metabolically inactive cultures as types. The Tokyo Code, also known as the "purple Code", foreshadowed the new and daringly modern idea of mandatory registration of future names and all but embraced the concept of stabilized lists of names in current use.

The Section in St Louis did not see fit to move further along that road, even reversing courses set at Yokohama six years before. Obviously, the pace of development of the Code had been too rapid for a hard core of nomenclatural practitioners to follow. The Section, in the perfectly sound logic of Reaction, therefore denied implementation to a tested and functional system for the registration newly proposed names, refused discussing the principle of protection of names in current use, and opposed most suggestions aiming at a harmonized terminology in biological nomenclature. This is an understandable response, not in itself a cause for worry. If one looks dispassionately at the ups and downs of World's history, and of biological nomenclature, one may safely anticipate that, after a truce, the now defeated proposals, or similar ones, will find favour at some future Congress.

We have, however, been saddened by the context in which these decisions took place. Passion in nomenclatural discussions is fine and (which is perhaps surprising with as dry a subject) has a solid tradition of long standing; but hatred has not. The Jacobine frenzy with which the Section was induced to eradicate all traces of registration from the Tokyo Code is we believe unprecedented. The refusal to listen to others, to let contradictory arguments be exposed and explained, has worried us deeply. With such a large and largely novel audience, nomenclature had a unique chance to prove itself a rational discipline. In this it has failed.

Perhaps, then, the failure is ours, who should have guided and advised the Section in its debates. Accepting this failure, we decided not to seek reappointment in our nomenclatural functions. If anyone, John McNeill, the new Rapporteur, has the skills and instinct needed to bring nomenclature forward in the new Millennium. In this, we wish him every success.

To you, the user, we now entrust the St Louis Code; the "black Code", as you may call it if you feel that the cover colour has meaning. And perhaps it has, symbolizing the silver stripe of hope set against the sombre background of Reaction (rather than mourn).


Berlin and London, 31 March 2000

Werner Greuter

David L. Hawksworth


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