Botanischer Garten und Botanisches Museum, Berlin-Dahlem Botanischer Garten und Botanisches Museum, Berlin-Dahlem

NCU-3. Names in Current Use for Extant Plant Genera

NCU-3. Names in Current Use for Extant Plant Genera

Printed edition: Introduction

Original text from the printed edition of NCU-3.


Introduction | Coverage | Nomenclature | Spelling and homonymy | Gender | Author and literature citations | Basionym citation | Type citation | Taxonomic disposition and index | A caveat and outlook | Literature cited


The plan to compile a list of currently used generic names of plants first took shape at an IUBS-sponsored exploratory ad-hoc meeting held at the International Mycological Institute at Kew on 22-23 April 1988. There it was generally agreed that such a list, especially if granted privileged nomenclatural status, would be the ideal means to make plant nomenclature more stable and more secure. The conclusions of that meeting (see Hawksworth & Greuter, 1989a, b), having been approved and commended by the IUBS XXIII General Assembly in November 1988 in Canberra (Di Castri & al., 1989), resulted in the official set-up of a Special Committee on Plant Names in Current Use, with two subcommittees, by the General Committee for the Nomenclature of Plants - the body which, between, International Botanical Congresses, has authority in matters of botanical nomenclature (Nicolson, 1989). The plans and ideas that had been formulated at the 1988 ad-hoc meeting were further discussed and refined at a number of Special Committee meetings and at two public workshops, one in Canberra in November 1988, the other in College Park, Maryland, during the IV International Congress on Systematic and Evolutionary Biology, on 2 July 1990. ICSEB IV explicitly supported the botanical Names in Current Use project, along with parallel initiatives by zoologists, in its "Resolution [No. 7] urging increased stability in the names of organisms". A synthesis of the NCU project and of correlated nomenclatural proposals (Greuter, l991c) was presented and discussed at the symposium on "Improving the Stability of Names: Needs and Options" at Kew in February 1991 (Hawksworth, 1991).

The detailed history of the present list can be looked up in the "Names in Current Use" column published in Taxon at regular intervals (Greuter, 1991a, b; 1992 a, b; 1993a). In short, draft lists of generic names believed to qualify as being in current use were generated for each of the major taxonomic groups (fungi, algae, bryophytes, pteridophytes, spermatophytes, and fossils) by preliminary selection from the "Index nominum genericorum" database. This selection was operated by members of the NCU Committee, often in close consultation with others, on the basis of group lists generated from the database. P. C. Silva (Berkeley) took care of the algae, P. M. Kirk (IMI Kew, now Egham) of the fungi, G. Zijlstra (Utrecht; assisted by R. Grolle, Jena, for the liverworts, and initially by M. J. Crosby, St. Louis, for the musci) of the bryophytes; R. K. Brummitt (Kew) of all vascular plants; and M. C. Boulter (London), in collaboration with W. G. Chaloner, of the plant fossils. The downloading of the data from the ING database and generation' of a master copy of the drafts was undertaken by E. R. Farr (Washington). The IAPT office in Berlin cared for the world-wide distribution of the drafts to 28 major botanical institutions serving as depositaries throughout the world, to the relevant Permanent Committees on nomenclature, and on demand to individual specialists. The lists and indexes covered 1375 pages in total, not counting covering letters and introductory matter, and were mailed in five portions between 29 May and 8 October 1991. R. H. Zander (Buffalo) arranged for the possibility of electronic access to the draft lists through Internet and the "Taxacom" server (Zander, 1991).

As is often the case with large scientific enterprises, the difficulties as well as the time and labour required to overcome them were initially underestimated. The data assembled and stored in the context of the Index nominum genericorum (plantarum) (Farr & al., 1979, 1986), having been contributed by many different persons through several decades, were by far not as uniform and reliable as we had trusted them to be. The draft lists accordingly were far from perfect and were critically received by botanists at large. In the case of the fungi a second version of the draft was produced by the IMI in the fall of 1991, for specialists to consult. Apart from the very numerous comments and suggestions received (see above) that had to be taken care of and incorporated by the Committee members responsible for the relevant groups, a huge effort of standardisation and checking of critical data was still required. Most of this occurred during the last six weeks in Berlin, as will be detailed below.

The list now before you owes much, not only to the persons just mentioned but to all those who commented on the drafts and whose names are mentioned on the previous pages: they all deserve our thanks for the time, skill and energy they devoted to improving it. Some persons must however be singled out for the special nature and importance of their contribution. After a fortnight's stay in Berlin, E. Parmasto (Tartu) presented us with a complete revision of the Aphyllophorales list. In the final rush toward completion, R. L. Moe, then back in Berkeley, selflessly assisted Paul Silva in updating the entries for the algae. R. E. G. Pichi Sermolli (Montagnana Val di Pesa) made an outstanding contribution to the pteridophyte list. R. J. Hnatiuk in Canberra and K. Iwatsuki in Tokyo undertook to distribute the draft lists to all interested parties in their respective countries, the latter also centralizing and co-ordinating the feedback; he was assisted by J. Sugiyama (Tokyo) for the fungi and I. Inouye (Tsukuba) for the algae. Combined comments representing the collective contribution of several staff members were also received from the National Botanical Institute, Pretoria; from the Conservatoire botanique de la Ville de Genève (H. M. Burdet); and from the Rijksherbarium in Leiden (P. Baas). A particularly valuable aid, for the spermatophytes, was an exhaustive comparative analysis of two brand-new generic inventories (Brummitt, 1992; Gunn & al., 1992) prepared and submitted by J. H. Wiersema (Beltsville).

The data file received in Berlin for final editing had been prearranged by Ellen Farr as well as was possible, bearing in mind the limitations of the ING database, in order to keep the necessary rearrangements at a reasonable level. At an early stage she had prepared a file with book and journal titles, in alphabetical sequence, which enabled N. Kilian (Berlin) to uniformize their citation and abbreviation. The standardisation of author abbreviations (see below) was taken care of by Paul Kirk, for all groups, with the aid of a specially devised computer program. D. H. Nicolson (Washington) provided an exhaustive list of generic names ending in -ma, each with its appropriate grammatical gender. Dick Brummitt, whom I had the pleasure of hosting in Berlin, at the end of February, for' a week of intense joint work on the vascular plant list, has ever since been extremely helpful and obliging in checking the odd reference in the Kew library and providing corresponding photostats; he also managed to obtain quick and authoritative opinions from the Committee for Spermatophyta, managed by him, on tricky individual questions of parahomonymy and validity of names.

In a general way, the successful completion of this project in the last few weeks of final rush would not have been possible without modern computing and communication technology. There was a steady flow of phone calls, fax and e-mail messages between Berlin, Kew, Egham, Berkeley and Washington, and most importantly, there was a group of people prepared to be bothered at any hour of the day and willing to respond by return to the odd and always urgent question that might arise at this end.

The final sentence of this eulogy must beyond doubt be devoted to Norbert Kilian and Brigitte Zimmer here in Berlin who, in the very moment in which these lines are being written, are struggling around the clock to feed in the last corrections and to have the master copy printed. If, as I trust, this book can be presented timely at the beginning of the Nomenclature Sessions, on 23 August in Tokyo-Yokohama, the credit will be theirs.


Generic names applying to all groups falling under the provisions of the International code of botanical nomenclature (Greuter & al., 1988) have been considered for inclusion, with a single but major exception: fossil plants. These too were originally to be included, but the idea had to be abandoned for the time being due to the rather chaotic state of the nomenclature of plant fossils. Thanks are nevertheless due to those who have contributed to compiling the circulated draft list of fossil names, and to all who cared to comment on it. Hopefully their efforts will not have been vain but will result in a better list of generic names of fossils, to be published at a later date.

The decision to omit fossil genera was not taken lightly, and not without the endorsement of the palaeobotanists concerned. There is a provision, in Art. 58 of the Code, to the effect that names based on fossil types do not compete for priority with names of living organisms, which means that protection of names of extant taxa alone cannot adversely affect fossil nomenclature (unless later homonyms of names in use for fossils were to be thus protected, which we made sure will not happen with the present list). This made inclusion of names of fossil plants less cogent. However, Art. 58 does not apply in the case of the algae, and a particular effort was therefore made to include those generic names based on fossil algae that apply to still extant genera and are in use for living taxa. After screening a large selection of generic names of fossil dinocysts and diatoms generated by Mike Boulter from his "Plant fossil record" database, no more than 10 diatom genera remained that were found to belong to this category. (They are: Actinella, Asterolampra, Campylodiscus, Delphineis, Denticulopsis, Hyalodiscus, Progonoia, Pseudotriceratium, Sheshukovia, and Xanthiopyxis.)

The most important and most delicate point regarding coverage was obviously the question, what is a "name in current use"? The Special Committee on Names in Current use has, at an early stage, provided a pragmatic and practicable definition in one its working documents. "Names in current use are legitimate names adopted in the most recent revision (if any) of the corresponding group, or in a recent flora within whose limits a given taxon occurs, or, failing this, they are the names that one would adopt, or that other botanists would likely adopt, when referring to a given taxon. Criteria for inclusion in NCU lists must be pragmatic and flexible, and the lists must certainly allow for those alternative taxonomies that are currently employed. The question may also be asked the other way round: Which names are not to go on a NCU list? The following 'negative' categories have been identified: (a) names that are either completely forgotten, or that are unused because universally considered as taxonomic synonyms; (b) names that are illegitimate either as junior homonyms or as being nomenclaturally superfluous, unless they are so well established that their conservation is desirable; (c) names that cannot be typified or whose type cannot be interpreted, unless, again, their present widespread use warrants their being retypified; and (d) names that have been used in a wrong sense and have become meaningless or misleading, and that qualify for rejection under Art. 69 of the Code, unless their conservation in the wrong but traditional sense offers a better solution."

It would be unrealistic to expect, and dishonest to claim, that these criteria have been consistently applied exactly in the same way by all who have contributed to the lists. Yet the underlying philosophy is clear, and so is the general policy that has been applied. Listed names are not recommended for use on the basis of a taxonomic judgement but are declared to be available for use by those who need them. They are considered for all events and purposes to be legitimate names that have been validly published at the quoted date and with the stated authorship - although this cannot be guaranteed (and will undoubtedly prove to be incorrect in individual cases) unless they are granted the special kind of nomenclatural protection that has is being sought for them. On the other hand, those names that are not listed are not thereby doomed. Some have doubtless been just plainly forgotten, and others that are presently believed to be synonyms may prove useful in the future as knowledge progresses or fashion changes. The present list will have to be updated by the addition of newly published names and of forgotten older ones, and mechanisms for such updating have been and are being considered (Hawksworth, 1992).

Coverage in time has been clearly defined: no names published on or after 1 January 1991 have been admitted to the list. Names published up to the end of 1990 do however qualify and have indeed been listed if validly published and legitimate. The youngest name on the list, that happens to be the only one published on 31 December 1990, was proposed for a rubiaceous genus: Anthorrhiza C. R. Huxley & Jebb.

The present list comprises exactly 28,041 entries of which 7241 pertain to the fungi, 3990 to the algae, 1382 to the bryophytes, 456 to the pteridophytes, 83 to the gymnosperms, 11,617 to the dicots, and 3272 to the monocots. A comparison with the number of items presently stored in the ING database (including spelling variants and illegitimate names) shows that 52.5 % of the ING names are considered to be in current use. This rate varies considerably between groups, being lowest for the spermatophytes (46 %) and highest for the algae (72 %), with the pteridophytes (51 %), fungi (59 %) and bryophytes (70 %) lying in-between.


The provisions of the Code have been scrupulously followed in cases of doubt, but where no doubt was apparent we avoided to ask questions. The purpose of a list that aims at bringing stability cannot be to enforce changes for no good purpose. In many cases, where the available data were incomplete or inconsistent, the sources had to be checked. Some entries had indeed to be modified, or worse deleted, since the name was found not to have been validly published in the cited place. We have not yielded to the temptation of consciously bending the rules in such cases, but at the same time we have tried to avoid situations in which such a temptation was likely to arise.

All names listed as conserved in Appendix IIIA of the Code have been faithfully listed (allowing for purely editorial corrections), except of course the names of fossil genera. (The single apparent omission that an attentive reader might spot, Pantoczekia in the Bacillariophyceae, does in fact refer to a fossil diatom genus with no extant species.) Reference to the corresponding rejected names has been added only when these names are themselves listed as being in current use, as may happen with rejected taxonomic synonyms.

Names proposed for conservation but not yet conserved by Congress action were treated in either of two ways. When the permanent committee for the group concerned had already voted to recommend the proposal, the entry conforms to that recommendation and includes the words nom. cons. des. (nomen conservandum designatum). This applies irrespective of whether or not the General Committee has already approved the recommendation, and even when no published committee report yet exists (we are grateful to the committee secretaries for having provided last minute information on committee votes in several cases). It also applies to entries listed with an asterisk in the Berlin Code, and even (with the des. placed in square brackets) to two names of which the conservation had been approved in Berlin but which were inadvertently omitted from the printed Code. When a proposal is still under consideration, the phrase nom. cons. prop. (nomen conservandum propositum) was added, and circulated committee comments were taken into consideration as appropriate. Needless saying, rejection of a proposal by the relevant committee is also taken into account.

Spelling and homonymy

We were cautious in correcting faulty original spellings of generic names, a matter on which no clear ruling exists in the Code. Wrong or awkward spellings that had come into use were maintained unless a Committee instructed otherwise. The case of the Australian "daisy" Brachyscome/Brachycome is a good example, on which the Committee vote ended in a tie so that the incorrect original spelling has now to be used. The Index nominum genericorum consistently gives preference to the original spelling, even when it is rather unfamiliar, and unless we were advised to the contrary this has been maintained. We have however as a rule accepted those corrections that are advocated by the recent, authoritative Kew list of vascular plant genera (Brummitt, 1992).

It has proved impossible to correct all misspellings of cited type species names, but we have done so at least in the case of the -i/-ii endings for which a clear ruling exists. We have also corrected wrong terminations of adjectival epithets in those instances in which the gender of the generic name has been specified (see below). Other corrections of gender, of erroneous connecting vowels, and of misspellings (including typographical errors originating from the ING database), were made occasionally but not methodically. We cannot therefore vouch for the correct form of the names cited under the type entry.

We have eliminated the diaeresis although its use is declared permissible by the Code (Art. 73.6). The main reason was not the difficulty it causes for automatical alphabetic sorting - with this we could have coped - but its completely erratic use in the ING database, which could not have been made consistent without extensive bibliographical and linguistic searches. We therefore decided to concentrate on more essential matters than such optional pronunciation helps that are moreover handled differently under different language traditions (the English sometimes use a diaeresis in the vowel pairs -oö- and -eë-, and the French in -oï-).

We saw no useful purpose in citing faulty original spellings when they differ from the adopted spelling. Such indications are, we feel, at best useless and at worst insulting for the original authors who may have blundered. This is a list of valid names, and variant spellings are defined by the Code (Art. 75.1) not to be validly published.

Entries of later homonyms, unless conserved or proposed for conservation, were eliminated radically in all cases in which the earlier homonym is listed as being in use. Repeated checks, first in Washington then in Berlin, were carried out to this effect. We were surprised at the number of deletions in which they resulted. No effort has been made to unearth unused, perhaps illegitimate earlier homonyms of names in current use, but of course when legitimate replacement names for the latter had already been proposed by others they were given preference.

Confusingly similar names, often designated as parahomonyms, were a difficult chapter. In a number of cases it was possible to obtain quick and informal advice from the Committee for Spermatophyta, which we then followed, on whether or not two similar names are to be regarded as confusable under Art. 64.3 of the Code. We noticed a general trend in that Committee to deny confusability in cases in which the older of two names was illegitimate or completely unused, and also when the names pertain to widely different taxonomic groups and have been consistently spelled differently in the past. This trend we took as a guideline. In fact, we have not deleted any potential later parahomonym without instructions from the pertinent Committee.


Knowing that grammatical gender of generic names is often difficult to assess for botanists not trained in the classical languages, and that usage in literature may vary, we had at an early stage envisaged to provide guidance on this question through the present list. It has not been possible to include indication of gender for all listed names, and in a majority of cases gender is anyhow uncontroversial and no pressing need for guidance exists. We have therefore concentrated on categories of names that pose problems. Time was insufficient for considering the large bulk of names ending in -us (mostly masculine but including many feminine tree designations) and -is (usually feminine but not seldom masculine), and for a number of rarer endings such as -o, -i, -ps, etc.

Gender indication is provided for all names covered by the provisions and examples of Art. 76 of the Code, and for all those ending in either -as, -es, -ma, -ne, -on, -x, or -ys. The largest and perhaps most involved of these is the group of names ending in -ma, which were dealt with by Dan Nicolson on the basis of an inversely alphabetised name list generated by Ellen Farr. I took care myself of the other endings. Gender indication could eventually be included for 4388 names, almost 16 % of the total, of which 1226 were found to be masculine ["(m.)"], 1329 feminine ["(f.)"], and 1833 neuter ["(n.)"]. In several cases the gender of the epithet of the type species name had to be corrected accordingly.

At this point I must insist on the fact that the gender indications included in this list are the result of personal judgement by two individual persons. They will hopefully be found to be sound enough to provide useful guidance, but they neither have the force of law nor are they yet mature to become an approved standard. The rationale followed in the assessment of gender is too complex to be explained in the frame of this introduction but will be published in some detail in forthcoming issues of the journal Taxon. On the basis of subsequent discussions it will we hope be possible to correct any mistakes, improve the basic criteria, and extend them to other names as well.

Author and literature citations

Authors' names were abbreviated in conformity with the new Kew standard (Brummitt & Powell, 1992). The abbreviation was done mechanically at the International Mycological Institute in Egham by Paul Kirk, on the basis of the spelled out author names contained in the ING database. The writing of an apposite computer program required quite some thought and skill since author names appear in different data fields including basionym citation and indication of type. A number of author names were dubious or ambiguous as listed and required special checking at the source, mainly done by Norbert Kilian, and subsequent manual treatment. Some additions to the Kew list were found necessary and a small number of corrections (as in the case of Grunow misspelled "Grunov"), but in a general way we found that standard to be admirably complete and accurate. The standardization and abbreviation of titles of books follows TL-2 (Stafleu & Cowan, 1976-1988; Stafleu & Mennega, 1992), that of journal titles, B-P-H (Lawrence & al., 1968; Bridson & Smith, 1991). Titles not mentioned in these source works have been treated by analogy, after verification either through other bibliographical devices or by direct consultation of the source; only a handful of references were not tracked in one way or another. This standardisation was the domain of Norbert Kilian, working on a list of citations generated by Ellen Farr from the ING database. We have to admit, though, that at some intermediate stage ING items were incorporated into the NCU file without previous title standardisation and that it was not possible to track them all in the aftermath, so that the odd entry may still be found that does not conform to our standards.

Details of conventions used for citation purposes have been explained earlier in a similar context (Greuter, 1993: 9-12) and need not be repeated here. May it suffice to point out that when the (suitably abbreviated) names of the authors of generic names are followed by a comma, they are also the authors or editors of the publication in which the protologue appears; if after the author citation the particle "in" appears instead, what follows is either the title of a journal or anonymously published serial work, or the reference to a book with a different authorship. That reference is not considered to be part of the nomenclatural author citation but an independent bibliographic entry, and author names appearing after the "in" are not therefore abbreviated.

Since illustrations in the protologue in most cases do not contribute to the valid publication of generic names, reference to plates or figures has as a rule been omitted. Normally the reference is to the descriptive text only; when the text appears on unnumbered pages accompanying a numbered plate, it is referred to by the expression "ad t....". Only exceptionally (when an illustration with analysis, published independently from - perhaps ahead of - corresponding descriptive text, serves as surrogate for a descriptio generico-specifica, as permitted prior to 1908 under Art. 42.2 of the Code) is reference made to the illustration itself.

Dates of publication are given as exactly and accurately as possible, based on information in TL-2 and in all other available sources, including of course the publication itself (see the Code, Art. 30.1, second sentence). However, alleged dates of publication that sometimes appear on title pages, but are different from the nomenclaturally relevant date on which actual publication occurred, are consistently and consciously omitted. Unfortunately, information on exact publication dates is as yet far from complete, since in many cases it was not possible to consult the original publication.

Preprints of journal articles without pagination of their own are considered as portions of the journal issued at the preprint date and are therefore cited from the journal. Dual citations were allowed only exceptionally, (a) for publications with a dual title, (b) for parallel, simultaneous editions of a work (e.g. as independent book and in a journal, or in two different formats), or (c) for different publications when the relative priority is uncertain.

Basionym citation

Hundreds of basionym references had to be added that were absent from the ING database. This was done by Norbert Kilian, with the aid of Paul Kirk, Dick Brummitt, and K. Iwatsuki when the data were unavailable in Berlin. To date no entry remains on the list in which a parenthetic authorship is given but no basionym is cited for a generic name. Needless saying, considerable time and effort were needed to achieve this goal.

Among the special problems encountered the cases of spelling differences deserve special mention. As a rule the basionym epithet and the generic name, when different, were treated as variants, one of which (not necessarily the earlier one) was considered to be correctable. If, however, the epithet of a purported basionym had the form of a plural adjective rather than the same form as a generic name (Code, Art. 21.2) we judged that a transfer was not possible; the generic name was then considered as an avowed substitute, and the alleged basionym as a replaced synonym.

Substituted synonyms (syn. subst.) are not as a rule cited. There are several reasons for this omission. First, this kind of information was only exceptionally present in the ING database, and there is no easy means of ascertaining whether and where it is lacking. Second, the distinction between an avowed substitute (nomen novum) and the name of a new taxon is one of the greyest among the grey areas of the Code. And third, the presence of a replaced earlier synonym does not bear on either the date or authorship of a generic name, so that lack of the corresponding information hardly affects the usefulness of this list. There is however one situation in which a "Syn. subst." entry was added: when for a post 1957 name no type could be mentioned since no holotype had been indicated. Such a name could easily be thought not to be validly published, which would indeed be the case if it had been proposed as the name of a new taxon not as a substitute for an earlier, validly published name.

Some purported basionyms were found not to be validly published, so that the parenthetic author citation had to be deleted after the generic name. Interestingly there is no parallel to the "descriptio generico-specifica" situation for the subordinate ranks, in the Code, so that the description of a single, new species included under a new subdivision of a genus cannot by itself validate the latter's name.

Type citation

Types have been designated for almost 95 % of the listed names (100 % for the liverworts, pteridophytes and gymnosperms; but only 87 % for the mosses). There are 1462 entries left with "Type: not designated", and an additional 11 with "Type: to be designated". The latter expression is used when the previously designated type is either debatable or clearly inappropriate, and indeed some of the corresponding names are the subject of a conservation proposal that would affect their typification.

Type citation basically follows the model of Appendix IIIA of the Code, which is also the style normally used in the Index nominum genericorum. Types are always indicated in the form of validly published species names (standing for their respective types), except in the case of a few nomina conservanda and names designed to become such, when the conserved type specimen is listed. As a rule the name used in the protologue is cited first, followed in parentheses by its basionym or replaced synonym, if any; and if the first mentioned name is illegitimate, by its legitimate homotypic synonym in the corresponding genus, if it exists. No heterotypic synonyms are listed, not even when they are universally considered as the correct name for the "type species", since such synonymy is nomenclaturally irrelevant and subject to taxonomic judgement.

Post 1957 names of new genera must be holotypified in order to be validly published (but see the previous chapter for the special case of avowed substitutes), and we were careful to provide type citations for all of them. Earlier names may have either holotypes or lectotypes, but we did not try to make that distinction, nor did we endeavour to give references to the (presumed) earliest lectotype designations. The reasons for this omission, which many may well resent; are multiple. Due to changes in the relevant rules at recent International Botanical Congresses, Berlin in particular, lectotype designations referred to in the Index nominum genericorum are all in need of being reviewed. Doing so would be a gigantic task, and would be both unrewarding and undesirable. It is not our wish to encourage in any way endless and sterile controversies over earliest effective lectotype choices. If the types listed here are found to appropriately reflect the current application of the names concerned they should better be left unchallenged; if not, they should be changed irrespective of nomenclatural technicalities, by conservation if need should be.

Taxonomic disposition and index

For nomenclatural purposes it is irrelevant to which higher ranking taxon an entry may pertain. Indications of taxonomic disposition are a matter of personal judgement not of nomenclatural rules. Nevertheless we felt that adding an indication of taxonomic affiliation to each entry and, conversely, providing an index of listed generic names by families or higher classification units would cover a need and add to the usefulness of our book. We were confirmed in our belief by the many critical reactions to taxonomic misplacements and inconsistencies which, originating from the ING database, appeared in the circulated draft lists.

We did not want to present forefront taxonomic opinions which mostly would not be our own anyway, but to provide a solid, traditional frame that would be meaningful for most and familiar to many. We thus abandoned at an early stage the idea of providing the same degree of taxonomic resolution for all groups, since it appeared that the systematics in some cases are still in constant flux at either family or ordinal level, or both. The criteria applied will be obvious from the index and are but briefly outlined here.

Whereas the two large fungal classes, Ascomycetes and Basidiomycetes, have been digested in orders and families hierarchically (allowing for some genera unplaced as to family and listed directly under the order), the middle sized classes (Chytridiomycetes, Myxomycetes, Oomycetes, Trichomycetes, Zygomycetes) were split into families only and the smaller ones (Acrasiomycetes, Agonomycetes, Hyphochytridiomycetes, Labyrinthulomycetes, Plasmodiophoromycetes), mostly considered to consist of a single family, were left undivided. The imperfect fungi were distributed among two large form classes, Coelomycetes and Hyphomycetes, without further subdivision. Paul Kirk at the IMI, advised by D. N. Pegler of Kew Gardens for the Basidiomycetes, has assumed lone responsibility for this classification.

After due consideration, if was felt premature to attempt classifying the algae below the level of class. In fact there are a dozen of algal genera for which not even class membership can be given, some perhaps forming classes of their own. The choice and delimitation of the 28 classes recognized in the index has been taken care of by Paul Silva.

In the bryophytes, the musci and hepaticae have been classified family-wise: the latter by Gea Zijlstra using the published system of Grolle (1983), the former as they are placed in the ING database since no bryologist apparently volunteered to provide an update. We are told that the genera of musci are the least well treated part of this inventory in several respects, but no concrete suggestions of improvement were made (and not even all comments received were made available to the editorial team by those to whom they had been addressed).

For the vascular plants, we had to conclude that by and large the only practical and practicable solution was to adopt the family outlines from the latest edition of Engler's Syllabus (Melchior & Werdermann, 1954; Melchior, 1964). It may be out of date in some respects, yet the solutions it presents are more familiar than those of any of its more recent counterparts. True, splitting the old protean Saxifragaceae, Liliaceae, and Polypodiaceae is now the fashion, but on how exactly to split them opinions still widely diverge: leaving them together may please no modern specialist, but splitting them in a given way will displease all but one. The most important point, perhaps, is that this list, in our intent, will mainly serve to trace names, not to classify taxa. For the latter purpose Brummitt's (1992) recent compendium offers a better tool, with which the present book was never designed to compete.

Naturally, we did and could not follow Engler's Syllabus blindly and uncritically. Knowledge progresses as time passes, and some genera now forming families of their own were either unknown or went unnoticed thirty years ago. The following families not mentioned in the Syllabus have thus been taken up: Alsenosmiaceae, Alzateaceae, Aralidiaceae, Emblingiaceae, Greyiaceae, Hanguanaceae, Huaceae, Oncothecaceae, Paracryphiaceae, Retziaceae, Rhynchocalycaceae, Saccifoliaceae, Simmondsiaceae, Stylobasiaceae, Surianaceae, Tepuianthaceae, and Ticodendraceae. On the other hand some splits that were recognized in 1964 but are not now upheld have been sunk, as follows: Dysphaniaceae in Chenopodiaceae, Henriqueziaceae in Rubiaceae, Hippocrateaceae in Celastraceae, Julianiaceae in Anacardiaceae, Picrodendraceae in Euphorbiaceae, Sarcospermataceae in Sapotaceae, and Theligonaceae in Rubiaceae. This leaves us with a total of 396 vascular plant families, unevenly divided between the pteridophytes (28), gymnosperms (12), dicots (302) and monocots (543. One of them, Leguminosae, has been further subdivided into three subfamilies.

A caveat and outlook

Having worked on this list during the last six weeks, and having watched others around me doing the same; having had a palpable measure of the amount of comments received and of careful screening done by well over 200 botanists worldwide; and having had the pleasure of experiencing the selfless and dedicated input and feedback from the whole editorial team, I can now confidently declare that the standard of consistency and reliability of this book is remarkably high. In the same time I am only too well aware of its not being perfect.

In the forefield of its publication this generic inventory has raised exaggerated expectations but also irrational fears. This is not (not yet) the bible of generic nomenclature that can rid us once and forever of nomenclatural struggles at this level. Still more vetting is needed before we can be sure that official approval of the list and blanket protection of all listed names will not result in a largish number of unwanted changes requiring conservation proposals. Yet the list is now in a general way a faithfu1 mirror image of the generic nomenclature in use today. The names listed here should not, I maintain, be allowed to be overthrown by sheer nomenclatural considerations unless this is necessary in the interest of nomenclatural stability and security.

In other words, some kind of interim protection of the generic names on this list is in my view the appropriate answer at this stage. This would permit easy unbureaucratic correction of shortcomings and gaps in the years to come, yet stop the nitpicking, too popular with some of us, that has had such devastating effects on the reputation of our science. Adoption of the NCU proposals by the Tokyo Congress, and referral of the present list to the new Permanent Committee thus established for further refining and updating in the six years to come, would I believe be the appropriate action to be taken at this stage. It will avoid too rash and drastic a change; it will give botanists throughout the world a new opportunity to test, amend and improve what must eventually become the joint achievement of us all; and, in the same time, it will spare botanical nomenclature the existential crisis it would otherwise likely be facing.

Berlin, 10 July 1993

Werner Greuter


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