III.  International rules of Botanical Nomenclature


Chapter IGeneral considerations and leading principles.

                Art. 1 Natural history can make no progress without a regular system of
nomenclature, which is recognized and used by the great majority of naturalists in
all countries.

                Art. 2 The prescriptions which govern the exact system of botanical nomen‐
clature are divided into principles, rules and recommendations.  The principles (art.
1–9, 1014 and 1518) are the foundation of the rules and recommendations.
The rules (art. 1058), destined to put in order the nomenclature which the past has
bequeathed to us, and to form the basis for the future, are always retroactive: names
or forms of nomenclature which are contrary to a rule cannot be maintained.  Recom-
mendations bear on secondary points, their object being to ensure for the future a
greater uniformity and clearness in nomenclature: names or forms of nomenclature
contrary to a recommendation are not a model to copy, but cannot be rejected.

                Art. 3 The rules of nomenclature should neither be arbitrary nor imposed
by authority.  They must be simple and founded on considerations clear and forcible
enough for everyone to comprehend and be disposed to accept.

                Art. 4 The essential points in nomenclature are:  1. to aim at fixity of
names;  2. to avoid or to reject the use of forms and names which may cause error
or ambiguity or throw science into confusion.

                Next in importance is the avoidance of all useless creation of names.

                Other considerations, such as absolute grammatical correctness, regularity or
euphony of names, more or less prevailing custom, respect for persons, etc., notwith-
standing their undeniable importance are relatively accessory.

                Art. 5 No custom contrary to rule can be upheld if it leads to confusion
or error.  When a custom offers no serious inconvenience of this kind, it may be a
ground for exceptions which we must however abstain from extending or copying.
Finally in the absence of rule, or where the consequences of rules are doubtful,
established custom becomes law.

                Art. 6 The principles and forms of nomenclature should be as similar as
possible in botany and in zoology; but botanical nomenclature is entirely independent
of zoological nomenclature.

                Art. 7 Scientific names are in latin for all groups.  When taken from
another language, a latin termination is given them, except in cases sanctioned by


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custom.  If translated into a modern language, it is desirable that they should pre-
serve as great a resemblance as possible to the original latin names.

                Art. 8 Nomenclature comprises two categories of names:  1. Names, or
rather terms, which express the nature of the groups comprehended one within the
other.  2. Names peculiar to each of the groups of plants that observation has
made known.

                Art. 9 The rules and recommendations of botanical nomenclature apply to
all classes of the plant kingdom, recent and fossil, with exceptions which are
expressly specified


Chapter IIOn the manner of designating the nature and the subordination

of the groups which constitute the plant kingdom.

                Art. 10 Every individual plant belongs to a species (species), every species
to a genus (genus), every genus to a family (familia) every family to an order (ordo),
every order to a class (classis), every class to a division (divisio).

                Art. 11 In many species we distinguish varieties (varietas) and forms (forma),
in the case of parasites special forms (forma specialis); and in some cultivated
species, modifications still more numerous; in many genera sections (sectio), in many
families tribes (tribus).

                Art. 12 Finally if circumstances require us to distinguish a greater number
of intermediate groups, it is easy, by putting the syllable sub before the name of a
group, to form subdivisions of that group. In this way subfamily (subfamilia) de-
signates a group between a family and a tribe, subtribe (subtribus) a group between
a tribe and a genus, etc. The arrangement of subordinate groups may thus be
carried, for wild plants only, to twenty-two degrees, in the following order:  Regnum
vegetabile.  Divisio.  Subdivisio.  Classis.  Subclassis.  Ordo.  Subordo.  Familia.  Sub-
familia.  Tribus.  Subtribus.  Genus.  Subgenus.  Sectio.  Subsectio.  Species.  Sub-
species.   Varietas.  Subvarietas.  Forma.  Forma specialis.  Individuum.

                If this list of groups is insufficient it can be augmented by the intercalation
of supplementary groups, so long as these do not introduce confusion or error.

                Example Series and Subseries are groups which can be intercalated between subsection
and species.

                Art. 13 The definition of each of these names of groups varies, up to a
certain point, according to individual opinion and the state of the science, but their
relative order, sanctioned by custom must not be altered.  No classification is ad-
missible which contains such alterations.

                Examples of inadmissible alterations are,  –  a form divided into varieties, a species containing
genera, a genus containing families or tribes.

                Art. 14 The fertilization of one species by another gives rise to a hybrid
(hybrida); that of a modification or subdivision of a species by another modification
of the same species gives rise to a half-breed (mistus, mule of florists).


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                I.   The arrangement of species in a genus or in a subdivision of a genus is made by means
of typographic signs, letters or numerals.  Hybrids are arranged after one of the parent species, with
the sign × placed before the generic name.

                The arrangement of subspecies under a species is made by letters or numerals; that of
varieties by the series of greek letters α, β, γ, etc.  Groups below varieties and also half-breeds are
indicated by letters, numerals or typographic signs at the author’s will.

                Modifications of cultivated plants should be associated, as far as possible, with the species
from which they are derived.

                Ibis.   In the case of parasites, especially parasitic fungi, authors who do not give specific
value to forms characterized from a biological standpoint but scarcely or not at all from a morpho-
logical standpoint, should distinguish within the species special forms (forma specialis, f. sp.) charac-
terized by their adaptation to different hosts.


Chapter III.   On the manner of designating each group

or association of plants.

Section 1.   General  principles;  priority.

                Art. 15 Each natural group of plants can bear in science only one valid

designation, namely the oldest, provided that it is in conformity with the rules of
nomenclature and the conditions laid down in articles 19 and 20 of section 2.

                Art. 16 The designation of a group by one or several names is not for
the purpose of describing the characters or the history of the group, but that we
may be understood when we wish to speak of it.

                Art. 17 No one should change a name or a combination of names without
serious motives, based on a more profound knowledge of facts, or on the necessity
of giving up a nomenclature that is contrary to rules.

                Art. 18 The form, number and arrangement of names depend on the nature
of each group, according to the following rules.

Section 2.   Point of departure for nomenclature;  limitation of principle of priority.

                Art. 19 Botanical nomenclature begins for the different groups of plants
(recent and fossil) at the following dates¹).

                a Phanerogamae and Pteridophyta, 1753 (Linnaeus, Species Plantarum,
ed. 1)

                b Muscineae, 1801 (Hedwig, Species Muscorum).

                c Sphagnaceae and Hepaticae, 1753 (Linnaeus, Species Plantarum, ed. 1).

                d Lichenes, 1753 (Linnaeus, Species Plantarum, ed. 1).

                e Fungi: Uredinales, Ustilaginales and Gasteromycetes, 1801 (Persoon, Synopsis
methodica Fungorum

                f Fungi caeteri, 1821–32 (Fries, Systema mycologicum).


                1) The starting points of the nomenclature of the following groups are reserved for
the consideration of the Congress at London, 1915. Schizomycetes (Bacteria), Schizophyceae (excl.
Nostocaceae), Flagellatae (incl. Dinoflagellatae), Bacillariaceae (Diatomaceae).


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                g Algae, 1753 (Linnaeus, Species Plantarum, ed. 1). Exceptions: Nosto-
caceae homocysteae, 1891–93 (Gomont, Nostocaceae homocysteae); Nostocaceae hetero-
cysteae, 1886 (Bornet et Flahault, Nostocaceae heterocysteae); Desmidiaceae, 1848
(Ralfs, British Desmidiaceae); Oedogoniaceae, 1900 (Hirn, Monographie und Ikono-
graphie der Oedogoniaceen).

                h Myxomycetes, 1753.

                It is agreed to associate genera, the names of which appear in Linnaeus’s
Species  Plantarum,  ed. 1,
  with  the  descriptions  given  of  them  in  the  Genera
, ed. 5 (1754).

                Art. 20 However, to avoid disadvantageous changes in the nomenclature
of genera by the strict application of the rules of nomenclature, and especially of the
principle of priority in starting from the dates given in art. 19, the rules provide a
list of names which must be retained in all cases.  These names are by preference
those which have come into general use in the fifty years following their publication,
or which have been used in monographs and important floristic works up to the
year 1890.

                For the guidance of palaeobotanists a double list is provided:  1º a list of
generic names of recent plants, duly published and generally admitted, which coincide
with older generic names in palaeobotany;  2° a list of generic names of fossil plants,
duly published and generally admitted, which coincide with older homonyms of recent
plants which have lapsed into synonymy, in order to prevent the latter being used
The lists form an appendix to the rules of nomenclature¹).

Section 3.   Nomenclature  of  the  different  kinds  of  groups.

§ 1.   Names of groups above the family.

                Recommendations.   The following suggestions as to the nomenclature of groups of higher
rank than the family will tend to clearness and uniformity.

                II.   Names of divisions and subdivisions, of classes and subclasses are taken from one of
their chief characters.  They are expressed by words of greek or latin origin, some similarity of
form and termination being given to those which designate groups of the same nature.

                Examples:  Angiospermae, Gymnospermae; Monocotyledoneae; Dicotyledoneae; Pteridophyta;
.  Among Cryptogams old family names such as Fungi, Lichenes, Algae, may be used for
names of groups above the rank of family.

                III.   Orders are designated preferably by the name of one of their principal families, with
the ending -ales.  Suborders are designated in a similar manner, with the ending -ineae.  But other
terminations may be retained for these names, provided that they do not lead to confusion or error.

                Examples of names of orders Polygonales (from Polygonaceae), Urticales (from Urticaceae),
Glumiflorae, Centrospermae, Parietales, Tubiflorae, Microspermae, Contortae.  Examples of names of
suborders:  Bromeliineae (from Bromeliaceae), Malvineae (from Malvaceae), Tricoccae, Enantioblastae.

§ 2.   Names of families and subfamilies, tribes and subtribes.

                Art. 21 Families (familiae) are designated by the name of one of their
genera or ancient generic names with the ending -aceae.


                1) The elaboration of this double list has been reserved for the Congress of 1915.


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                Examples:  Rosaceae (from Rosa), Salicaceae (from Salix), Caryophyllaceae (from Dianthus
), etc.

                Art. 22 The following names, owing to long usage, are an exception to the
rule:  Palmae, Gramineae, Cruciferae, Leguminosae, Guttiferae, Umbelliferae,
Labiatae, Compositae

                Art. 23 Names of subfamilies (subfamiliae) are taken from the name of one
of the genera in the group, with the ending -oideae.  The same holds for the tribes
(tribus) with the ending -eae, and for the subtribes (subtribus) with the ending -inae.

                Examples of subfamiliesAsphodeloideae (from Asphodelus), Rumicoideae (from Rumex);
tribes: Asclepiadeae (from Asclepias), Phyllantheae (from Phyllanthus); subtribes: Metastelmatinae (from
Metastelma), Madiinae (from Madia).

§ 3.   Names of genera and divisions of genera.

                Art. 24 Genera receive names, substantives (or adjectives used as substan-
tives) in the singular number and written with a capital letter, which may be com-
pared with our own family names.  These names may be taken from any source
whatever and may even be composed in an absolutely arbitrary manner.

                Examples:  Rosa, Convolvulus, Hedysarum, Bartramia, Liquidambar, Gloriosa, Impatiens, Manihot.

                Art. 25 Subgenera and sections also receive names, usually substantives and
resembling the names of genera.  Names of subsections and other lower subdivisions
of genera are preferably adjectives in the plural number and written with a capital
letter, or their place may be taken by an ordinal number or a letter.

                Examples.  –  Substantives: Fraxinaster, Trifoliastrum, Adenoscilla, Euhermannia, Archie-
, Micromelilotus, Pseudinga, Heterodraba, Gymnocimum, Neoplantago, Stachyotypus.  Adjectives:
Pleiostylae, Fimbriati, Bibracteolata, Pachycladae.


                IV.   When the name of a genus, subgenus or section is taken from the name of a person,
it is formed in the following manner:

                a When the name ends in a vowel, the letter a is added (for example Bouteloua after
Boutelou; Ottoa after Otto; Sloanea after Sloane
), except when the name already ends in a, in which
case ea is added (e. g. Collaea after Colla).

                b When the name ends in a consonant, the letters ia are added (thus Magnusia after
Magnus; Ramondia after Ramond), except when the name ends in er, in which case a is added
(e. g. Kernera after Kerner).

                c The spelling of the syllables unaffected by these finals is retained, even with the
consonants k and w or with groupings of vowels which were not used in classic latin.  Letters
which are unknown to botanical latin must be transcribed, diacritic signs are suppressed.  The german
ä, ö, ü become ae, oe, ue, the French é, è and ê become generally e.

                d Names may be accompanied by a prefix, or a suffix, or modified by anagram or
abbreviation. In these cases they count as different words from the original name.  E. g. Durvillea
and Urvillea, Lapeyrousea and Peyrousea, Englera, Englerastrum and Englerella, Bouchea and Ubochea,
Gerardia and Graderia, Martia and Martiusia.

                V.   Botanists who are publishing generic names show judgement and taste by attending
to the following recommendations:

                a) Not to make names very long or difficult to pronounce.


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                b) Not to use again a name which has already been used and has lapsed into synonymy

                c) Not to dedicate genera to persons who are in all respects strangers to botany, or at
least to natural science, nor to persons quite unknown.

                d) Not to take names from barbarous tongues, unless those names are frequently quoted
in books of travel, and have an agreeable form that is readily adapted to the latin tongue and to
the tongues of civilized countries.

                e) To recall, if possible, by the formation or ending of the name, the affinities or the
analogies of the genus.

                f) To avoid adjectives used as nouns.

                g) Not to give a genus a name whose form is rather that of a subgenus or section (e. g.
Eusideroxylon, a name given to a genus of Lauraceae, which, however, being valid, cannot be changed).

                h) Not to make names by the combination of two languages (nomina hybrida).

                VI.   Botanists constructing names for subgenera or sections, will do well to attend to the
preceding recommendations and also to the following:

                a) Give, where possible, to the principal division of a genus, a name which, by some modi-
fication or addition, calls the genus to mind (for instance, Eu placed at the beginning of the name,
when it is of greek origin, -astrum, -ella at the end of the name, when latin, or any other modi-
fication consistent with the grammar and usages of the latin language).

                b) Avoid calling a subgenus or a section by the name of the genus to which it belongs,
with the final -oides or -opsis: on the contrary reserve this ending for a section which resembles
another genus, by adding in that case -oides or -opsis to the name of that other genus, if it is of
greek origin, to form the name of the section.

                c) Avoid taking as the name of a subgenus or section a name which is already in use as
such in another genus, or which is the name of an admitted genus.

                VII.   When it is required to express a subgeneric or sectional name together with the
name of the genus and the name of the species, the name of the section is put between the others
in a parenthesis.  E.g. Astragalus (Cycloglottis) contortuplicatus.

§ 4.  Names of species and of subdivisions of species.

                Art. 26 All species, even those that singly constitute a genus, are designated
by the name of the genus to which they belong followed by a name (or epithet)
termed specific, usually of the nature of an adjective (forming a combination of two
names, a binomial, or binary name).

                Examples:  Dianthus monspessulanus, Papaver Rhoeas, Fumaria Gussonei, Uromyces Fabae,
Geranium Robertianum, Embelia Sarasinorum, Adiantum Capillus-Veneris Linnaeus has sometimes
introduced symbols in specific names, these must according to art. 26 be transcribed. Ex.: Scandix
Pecten-Veneris (= Scandix Pecten
); Veronica Anagallis-aquatica (= Veronica Anagallis).


                VIII.   The specific name should, in general, give some indication of the appearance, the
characters, the origin, the history or the properties of the species.  If taken from the name of a
person, it usually recalls the name of the one who discovered or described it, or was in some way
concerned with it.

                IX.   Names of men and women and also names of countries and localities used as
specific names, may be substantives in the genitive (Clusii, saharae) or adjectives (Clusianus, dahuricus).
It will be well, in the future, to avoid the use of the genitive and the adjectival form of the same
name to designate two different species of the same genus: for example Lysimachia Hemslyana
Maxim. (1891) and L. Hemsleyi Franch. (1895).


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                X.   Specific names begin with a small letter except those which are taken from names of
persons (substantives or adjectives) or those which are taken from generic names (substantives or adjectives).

                Examples:  Ficus indica, Circaea lutetiana, Brassica Napus, Lythrum Hyssopifolia, Aster novi-
, Malva Tournefortiana, Phyteuma Halleri.

                XI.   When a specific name is taken from the name of a man, it is formed in the follow-
ing way:

                a) When the name ends in a vowel, the letter i is added (thus Glazioui from Glaziou;
Bureaui from Bureau), except when the name ends in a, when e is added (thus Balansae from Balansa).

                b) When the name ends in a consonant, the letters ii are added (thus Magnusii from
Magnus; Ramondii from Ramond), except when the word ends in er when i is added (ex. Kerneri,
from Kerner).

                c) Syllables which are not modified by these endings retain their original spelling, even in
the case of the consonants k and w or groupings of vowels which are not used in classic latin.  Letters
foreign to the latin of botanists should be transcribed, and diacritic signs suppressed.  The german
ä, ö, ü, become ae, oe, ue, the french é, è and ê become, in general, e.

                d) When specific names taken from the name of a person have an adjectival form a similar
plan is adopted (Geranium Robertianum, Verbena Hasslerana, etc.).

                XII.   The same applies to the names of women.  These are written in the feminine when
they have a substantival form.

                Example Cypripedium Hookerae, Rosa Beatricis, Scabiosa Olgae, Omphalodes Luciliae.

                XIII.   In the formation of specific names composed of two or several roots and taken from
latin or greek, the vowel placed between the two roots becomes a connecting vowel, in latin i, in greek o;
thus we write menthifolia, salviifolia, not menthaefolia, salviaefolia.  When the second root begins
with a vowel and euphony demands, the connecting vowel is eliminated (e. g. calliantha, lepidantha).
The connecting ae is legitimate only when etymology demands (e. g. caricaeformis from Carica, may
be retained along with cariciformis from Carex).

                XIV. In forming specific names, botanists will do well to note the following recommendations:

                a) Avoid very long names and those which are difficult to pronounce.

                b) Avoid names which express a character common to all or nearly all the species of a genus.

                c) Avoid names taken from little known or very restricted localities, unless the species
be very local.

                d) Avoid, in the same genus, names which are very much alike, especially those which
differ only in their last letters.

                e) Adopt unpublished names found in travellers’ notes and in herbaria, attributing them to
the authors concerned, only when those concerned have approved the publication.

                f) Avoid names which have been used before in the genus, or in any closely allied genus,
and which have lapsed into synonymy (homonyms).

                g) Do not name a species after a person who has neither discovered, nor described, nor
figured, nor in any way studied it.

                h) Avoid specific names formed of two words.

                i) Avoid names which have the same meaning as the generic name.

                Art. 27 Two species of the same genus cannot bear the same specific name,
but the same specific name may be given in several genera.

                Example Arabis spathulata DC. and Lepidium spathulatum Phil. are valid as two names
of Crucifers; but Arabis spathulata Nutt. in Torr. and Gray cannot be maintained, on account of the
existence of Arabis spathulata DC., a name previously given to another valid species of Arabis.

                Art. 28 Names of subspecies and varieties are formed like specific names
and follow them in order, beginning with those of the highest rank.  The same holds

for subvarieties, forms, and slight or transient modifications of wild plants which


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receive a name or numbers or letters to facilitate their arrangement.  Use of a
binary nomenclature for subdivisions of species is not admissible.

                Examples:  Andropogon ternatus subsp. macrothrix (not Andropogon macrothrix or Andropogon
subsp. A. macrothrix); Herniaria hirsuta var. diandra (not Herniaria diandra or Herniaria
var. H. diandra); forma nanus, forma maculatum.


                XV.   Recommendations made for specific names apply equally to names of subdivisions of
species.  These agree with the generic name when they have an adjectival form (Thymus Serpyllum
var. angustifolius, Ranunculus acris subsp. Friesianus).

                XVbis.   Special forms are named preferably after the host species; if desired double
names may be used.  Examples Puccinia Hieracii f. sp. villosi, Pucciniastrum Epilobii f. sp. Abieti-

                Art. 29 Two subspecies of the same species cannot have the same name.
A given name can only be used once for a variety of a given species, even when
dealing with varieties which are classed under different subspecies.  The same holds
for subvarieties and forms.

                On the other hand the same name may be employed for subdivisions of
different species, and the subdivisions of any one species may bear the same name
as other species.

                Examples.  –  The following are admissible:  Rosa Jundzillii var. leioclada and Rosa glutinosa
var. leioclada; Viola tricolor var. hirta, in spite of the existence already of a different species named
Viola hirta The following are incorrect: Erysimum hieraciifolium subsp. strictum var. longisiliquum
and E. hieraciifolium subsp. pannonicum var. longisiliquum  –  a form of nomenclature which allows
two varieties bearing the same name in the same species.


                XVI.   Botanists are recommended to use as little as possible the privilege granted in the
second part of article 29, in order to avoid confusion and mistakes and also to reduce to a minimum
the necessary changes of name when the subdivisions of species are raised to specific rank or
vice versa.

                Art. 30 Forms and half-breeds among cultivated plants should receive fancy
names, in common language, as different as possible from the latin names of the
species or varieties.  When they can be traced back to a species, a subspecies or a
botanical variety this is indicated by a succession of names.

                Example Pelargonium zonale Mrs. Pollock.

§ 5. Names of hybrids and half-breeds (mules).

                Art. 31 Hybrids between species of the same genus, or presumably so, are
designated by a formula and, whenever it seems useful or necessary, by a name.

                The formula consists of the names or specific epithets of the two parents in
alphabetical order and connected by the sign ×.  When the hybrid is of known
experimental origin the formula may be made more precise by the addition of the
signs ♀, ♂.

                The name, which is subject to the same rules as names of species, is distin-
guished from the latter by absence of an ordinal number and by the sign × before
the name.


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                Examples:   ×  Salix capreola = Salix aurita  ×  caprea; Digitalis lutea ♀  ×  purpurea ♂;
Digitalis lutea ♂  ×  purpurea ♀.

                Art. 32 Intergeneric hybrids (between species of different genera) or pre-
sumably such, are also designated by a formula, and, when it seems useful or necessary,
by a name.

                The formula consists of the names of the two parents, in alphabetical order.

                The hybrid is associated with the one of the two genera which precedes the
other in alphabetical order.  The name is preceded by the sign ×.

                Example  ×  Ammophila baltica = Ammophila arenaria  ×  Calamagrostis epigeios.

                Art. 33 Ternary hybrids, or those of a higher order, are designated like
ordinary hybrids by a formula and a name.

                Example  ×  Salix Straehleri = S. aurea  ×  cinerea  ×  repens or S. (aurita  ×  repens)
×  cinerea.

                Art. 34 When there is reason to distinguish the different forms of a hybrid
(pleomorphic hybrids, combinations between different forms of collective species etc.)
the subdivisions are classed under the hybrid like the subdivisions of species under
a species.

                Examples:   ×  Mentha villosa  β  Lamarckii (= M. longifolia  ×  rotundifolia).  The prepon-
derance of the characters of one or other parent may be indicated in the formulas in the following
manner:  Mentha longifolia  >  ×  rotundifolia, M. longifolia  ×  <  rotundifolia, Cirsium supercanum
×  rivulare, etc. etc.  The participation of a particular variety may also be indicated.  Example:
Salix caprea  ×  daphnoides var. pulchra.


                XVII.   Half-breeds, or presumably such, may be designated by a name and a formula.
Names of half-breeds are intercalated among the subdivisions of a species preceded by the sign ×.
In the formula the names of the parents are in alphabetical order.


Section 4The  publication  of  names  and  the  date  of  each  name  or

combination  of  names.

                Art. 35 Publication is effected by the sale or public distribution of printed
matter or indelible autographs.

                Communication of new names at a public meeting, or the placing of names
in collections or gardens open to the public, do not constitute publication.

                Examples.  –  Effective publication without printed matter: Salvia oxyodon Webb and Heldr.
was published in July 1850 in an autograph catalogue and put on sale (Webb and Heldreich, Cata-
logus plantarum hispanicarum, etc. ab A. Blanco lectarum
, Parisiis, Jul. 1850 in folio).  –  Non-effective
publication at a public meeting: Cusson announced his establishment of the genus Physospermum
in a memoir read at the Société des Sciences de Montpellier in 1773, and later in 1782 or 1783 at
the Sociétè de Médecine de Paris, but its effective publication dates from 1787, in the Mémoires
de la Soc. Roy. de Médicine de Paris
, vol. V, 1re partie.

                Art. 36 On and after January 1, 1908, the publication of names of new
groups of recent plants will be valid only when they are accompanied by a latin


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                Art. 36bis On and after January 1, 1912, the publication of names of new
groups of fossil plants will be valid only when they are accompanied by a latin
diagnosis and by illustrations or figures showing the essential characters of the
object in question.

                Art. 37 A species or a subdivision of a species, announced in a work, with
a complete specific or varietal name, but without diagnosis or reference to a former

description under another name, is not valid.  Citation in synonymy or incidental

mention of a name is not effective publication, and the same applies to the mention
of a name on a ticket issued with a dried plant without printed or autographed diagnosis.

                Plates accompanied with analyses are equivalent to a description; but this
applies only to plates published before January 1, 1908.

                Examples.  –  The following are valid publications Onobrychis eubrychidea Boiss. Fl. or. II,

546 (1872) published with description; Panax nossibiensis Drake in Grandidier Hist. Phys. Nat. et
Polit. de Madagascar
, Vol. XXXV, t. V, III, 5e part., pl. 406 (1896), published in the form of a

plate with analyses; Cynanchum nivale Nym. Syll. fl. Eur. 108 (1854–1855) published with a

reference to Vincetoxicum nivale Boiss. et Heldr. previously described.  Hieracium Flahaultianum
Arv.-Touv. et Gaut., published in an exsiccata accompanied by a printed diagnosis (Hieraciotheca

gallica, nos. 935–942, 1903).  –  The following are not valid:  Sciadophyllum heterotrichum Decaisne
et Planch. in Rev. Hortic., ser. IV, III, 107 (1854), published without description or reference to a

previous description under another name; Ornithogalum undulatum Hort. Berol. ex Kunth Enum. pl.
IV, 348 (1843), quoted as a synonym of Myogalum Boucheanum Kunth l. c., the name adopted by
the author, is not a valid publication; when transferred to Ornithogalum, this species must be called

Ornithogalum Boucheanum Aschers. in Österr. Bot. Zeitschr. XVI, 192 (1866); Erythrina micropteryx
Poepp. quoted as a synonym of Micropteryx Poeppigiana Walp. in Linnaea XXIII, 740 (1850) is not
a valid publication; the species in question, when placed in the genus Erythrina must be called

Erythrina Poeppigiana O. F. Cook in U. S. Dep. Agr. Bull. n° 25, p. 57 (1901); Nepeta Sieheana
Hausskn. which appears without diagnosis in an exsiccata (W. Siehe, Bot. Reise nach Cicilien, n° 521,
1896), is not valid.

                Art. 38 A genus or any other group of higher rank than a species, named
or announced without being characterised conformably to article 37 cannot be regarded
as effectively published (nomen nudum).  The mere indication of species as belonging
to a new genus or of genera as belonging to a higher group, does not allow us to

accept the genus or group in question as characterised and effectively published.  An
exception is made in the case of the generic names mentioned by Linnaeus in the
Species Plantarum ed. 1, 1753, names which we associate with the descriptions in
the Genera Plantarum ed. 5, 1754 (See article 19).

                Examples.  –  The following are valid publications: Carphalea Juss. Gen. Pl. 198 (1789),
published with a description; Thuspeinanta Dur. Ind. Gen. Phaner., p. X (1888), published with a
reference to the genus Tapeinanthus Boiss. previously described; Stipa L. Sp. Pl. ed. 1, 78 (1753),

valid because accompanied by a description in the Genera Plantarum ed. 5, n° 84 (1754).  –  The
following are not valid: Egeria Neraud (Bot. Voy. Freycinet, 28 (1826), published without diagnosis

or reference to a description previously made under another name;  Acosmus Desv. mentioned inci-
dentally as a synonym of the genus Aspicarpa Rich. by De Candolle (Prodr. 1, 583 [1824]); Zatarhend
Forsk. Fl. Aeg. Arab., p. CXV (1775), based only on the enumeration of three species of the genus
Ocimum without indication of characters.

                Art. 39 The date of a name or of a combination of names is that of their
effective publication.  In the absence of proof to the contrary, the date placed on the


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work containing the name or combination of names is regarded as correct.  On and
after January 1st, 1908, the date of publication of the latin diagnosis only can be

taken into account in questions of priority in the case of recent plants; in the case
of fossil plants, on and after January 1st, 1912, it is the date of simultaneous publi-
cation of the latin diagnosis and a figure.

                Examples.  –  Mentha foliicoma Opiz was distributed by its author in 1832, but the name
dates from 1882 (published by Déséglise Menth. Op. in Bull. soc. étud. scient. Angers, 1881–1882,
210): Mentha bracteolata Op. Seznam, 65 (1852) without description, takes effect only from 1882,
when it was published with a description (Déséglise 1. c., 211). There is some reason for
supposing that the first volume of Adanson’s Familles des Plantes was published in 1762, but in
absence of certainty the date 1763 on the title-page is assumed to be correct.  The different parts of
Willdenow’s Species Plantarum were published as follows: vol. I, 1798; vol. II, 2, 1800; vol. III, 1,
1801; vol. III, 2, 1803; vol. III, 3, 1804; vol. IV, 2, 1806; and not in the years 1797, 1799, 1800,
1800, 1800 and 1805 respectively, as would appear from the title-page of the volumes: it is the
earlier series of dates which takes effect.  –  The third volume of the Prodromus florae hispanicae
of Willkomm & Lange, the title-page of which bears the date 1880, was published in four parts,
pp. 1–240 in 1874, pp. 241–512 in 1877, pp. 513–736 in 1878, p. 737 to the end in 1880, and
it is these dates which take effect.

                Recommendations.   Botanists will do well, in publishing, to conform to the following

                XVIII.   Not to publish a name without clearly indicating whether it is the name of a
family or a tribe, a genus or a section, a species or a variety; briefly, without expressing an opinion
on the nature of the group to which they give the name.

                XVIIIbis.   When publishing names of new groups to indicate carefully the subdivision
which is regarded as the type of the group: the typical genus in a family, the typical species in a
genus, the typical variety or specimen in a species.  This precaution will obviate difficulties of
nomenclature if at some future time the group in question becomes broken up.

                XIX.   To avoid publishing or mentioning in their publications unpublished names which
they do not accept, especially if the persons responsible for these names have not formally authorised
their publication (see Rec. XIV, e).

                XX.   When publishing names of new groups in works written in a modern language (floras,
catalogues etc.) to publish simultaneously the latin diagnoses and in palaeobotany also the figures,
which will make the names valid from the point of view of scientific nomenclature.

                XXbis.   In view of the special difficulties presented by the identification of fossil plants,
to give, in addition to the latin diagnosis a detailed description in french, english, german or italian.

                XXter.   In describing new groups of lower Cryptogams, especially among the Fungi or
microscopic plants, to add to the description a figure or figures of the plants, with details of
microscopic structure, as an aid to identification.

                XXquat.   The description of parasitic plants should always be followed by the indication
of the hosts, especially in the case of parasitic fungi.  The hosts should be designated by their
latin scientific names and not by popular names in modern languages, the signification of which is
often doubtful.

                XXI.   To give the etymology of new generic names and also specific names when the
meaning of the latter is not obvious.

                XXII.   To indicate precisely the date of publication of their works and that of the placing
on sale or the distribution of named and numbered plants when these are accompanied by printed
diagnoses.  In the case of a work appearing in parts, the last published sheet of the volume should
indicate the precise dates at which the different fascicles or parts of the volume were published, as
well as the number of pages in each.


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                XXIII.   When works are published in periodicals to require the editor to indicate on the
separate copies the date (year and month) of publication and also the title of the periodical from
which the work is extracted.

                XXIV.   Separate copies should always bear the pagination of the periodical of which they
form a part; if desired they may also bear a special pagination.


Section  5.   On  the  precision  to  be  given  to  names  by  the  citation

of  the  author  who  first  published  them.

                Art. 40 For the indication of the name or names of a group to be accurate
and complete, and in order that the date may be readily verified, it is necessary to
quote the author who first published the name or combination of names in question.

                Examples:  Simarubaceae Lindley, Simaruba Aublet, Simaruba laevis Grisebach, Simaruba
Aublet var. opaca Engler.

                Art. 41 An alteration of the constituent characters or of the circumscription
of a group does not warrant the quotation of another author than the one who first
published the name or combination of names.

                When the changes have been considerable, the words: mutatis charact., or
pro parte, or excl. gen., excl. sp., excl. var., or some other abridged indication, are
added after the citation of the original author, according to the nature of the changes
that have been made, and of the group in question.

                Examples:  Phyllanthus L. em. (emendavit) Müll. Arg.; Myosotis L. pro parte, R. Br.;
Globularia cordifolia L. excl. var. β.; etc.

                Art. 42 When a manuscript name has been published and referred to its
author, the name of the person who published it should be appended to the citation.
The same rule should be followed for names of garden origin when they are cited
as „Hort“.

                Examples:  Capparis lasiantha R. Br. ex or apud DC.; Streptanthus heterophyllus Nutt. in
Torr. et Gray; Gesnera Donklarii Hort. ex or apud Hook. Bot. Mag. tab. 5070.

                Art. 43 When, in a genus, a name is applied to a group which is moved
into another group where it retains the same rank, or to a group which becomes of
higher or lower rank than before, the change is equivalent to the creation of a new
group and the author who has effected the change is the one to be quoted.  The
original author can be cited only in parenthesis.

                Examples.  –  Cheiranthus tristis L. when moved into the genus Matthiola becomes Matthiola
R. Br., or Matthiola tristis (L.) R. Br.  –  Medicago polymorpha L. var. orbicularis L. when
raised to the rank of a species becomes Medicago orbicularis All. or Medicago orbicularis (L.) All.


                XXV.   Authors’ names put after names of plants are abbreviated, unless they are very short.

                For this purpose preliminary particles or letters that do not, strictly speaking, form part
of the name, are suppressed, and the first letters are given without any omission.  If a name of one
syllable is long enough to make it worth while to abridge it, the first consonants only are given
(Br. for Brown); if the name has two or more syllables, the first syllable and the first letter of the
following one are taken, or the two first when both are consonants (Juss. for Jussieu; Rich. for
Richard).  When it is necessary to give more of a name to avoid confusion between names beginning
with the same syllables, the same system is to be followed.  For instance two syllables are given


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together with the one or two first consonants of the third; or one of the last characteristic consonants
of the name is added (Bertol. for Bertoloni, to distinguish from Bertero; Michx for Michaux, to
distinguish from Micheli).  Christian names or accessory designations, serving to distinguish two
botanists of the same name, or abridged in the same way (Adr. Juss. for Adrien de Jussieu, Gaertn.
fil. or Gaertn. f. for Gaertner filius).

                When it is a well established custom to abridge a name in another manner, it is best to
conform to it (L. for Linnaeus, DC. for De Candolle, St.-Hil. for Saint-Hilaire).

                In publications destined for the general public and in titles it is preferable not to abridge.

                XXVbis.   The citation in parenthesis of the original author is especially useful in the
absence of synonymy or when the latter is a long one.  In palaeobotany the custom is always to
cite in parenthesis the original author of the epithet of a species or of a subdivision of a transferred

                XXVter.  The citation of authors earlier than the starting point of the nomenclature of a
group, is indicated when considered useful or desirable, preferably between brackets or by the use
of the word ex.  This method is especially applicable in mycology when reference is made to
authors earlier than Fries or Persoon.  Examples: Lupinus [Tournef. Inst. 392, t. 213 (1719)] Linn.
Sp.  ed. 1, 721  (1753)  and Gen.  ed. 4,  332, or Lupinus Tourn.  ex  L.  –  Boletus piperatus  [Bull
Hist. Champ. Fr. 318, t. 451 f. 2 (1791–1812)] Fries Syst. Myc. I, 388 (1821), or Boletus piperatus
Bull. ex Fries.

Section 6.   On  names  that  are  to  be  retained  when  a  group  is  divided,

remodelled,  transferred,  or  moved  from  one  rank  to  another,  or  when  two  groups

of   the   same   rank   are   united,   or   in   dealing   with groups   which   have   a   pleo-

morphic life-cycle.

                Art. 44 A change of characters, or a revision which involves the exclusion
of certain elements of a group or the addition of new elements, does not warrant
a change in the name or names of a group, except in cases provided for in article 51.

                Examples.  –  The genus Myosotis as revised by R. Brown differs from the original genus of
Linnaeus, but the name has not been changed, nor is any change allowable.  Various authors have
united with Centaurea Jacea L. one or two species which Linnaeus had kept distinct, the group thus
constituted must be called Centaurea Jacea L. (sensu ampl.) or Centaurea Jacea L. (em. Visiani, em.
Godron, etc.); the creation of a new name such as Centaurea vulgaris Godr. is superfluous.

                Art. 45 When a genus is divided into two or more genera, the name must
be kept and given to one of the principal divisions.  If the genus contains a section
or some other division which, judging by its name or its species, is the type or the
origin of the group, the name is reserved for that part of it.  If there is no such
section or subdivision, but one of the parts detached contains a great many more
species than the others, the name is reserved for that part of it.

                Examples.  –  The genus Helianthemum contained, according to Dunal (in DC. Prodr. 1.
266–284 [1824]), 112 well-known species distributed in nine sections, several of these sections have
since been raised to generic rank (Fumana Spach, Tuberaria Spach) but the name Helianthemum has
been kept for the divisions grouped round the section Euhelianthemum.  –  The genus Convolvulus
L. em. Jacq. was divided into two by Robert Brown in 1810 (Prodr. fl. Nov. Holl., pp. 482–484),
who gave the name Calystegia to one of the genera which at that time contained only four species,
and reserved the name Convolvulus for the other genus which contained a much larger number of
species.  –  In the same way Salisbury (in Trans. Linn. Soc. VI, 317 [1802]), in separating Erica
L. from the genus Erica, under the name Calluna, kept the name Erica for the large


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number of species left.  –  The genus Aesculus L. contains the sections Eu-Aesculus, Pavia (Poir.),
Macrothyrsus (Spach) and Calothyrsus (Spach), the last three of which were regarded as distinct
genera by their respective authors.  In the event of these genera being retained the name Aesculus
must be kept for the species Aesculus Hippocastanum L. as this is undoubtedly the type of the genus
founded by Linnaeus (Sp. pl. ed. 1, 344), as is seen by a comparison with Linnaeus, Hort. Cliff.
142, and early editions of the Gen. pl. (ed. 1, 310; ed. 2, 367); Tournefort’s name Hippocastanum
must not be used as was done by Gaertner (Fruct. ii. 135).

                Art. 46 When two or more groups of the same nature are united the
name of the oldest is retained.  If the names are of the same date, the author
chooses, and his choice cannot be modified by subsequent authors.

                Examples.  –  Hooker f. and Thomson (Fl. Ind. 67 [1855]) united the genera Wormia
Rottb. and Capellia Bl.; they gave the name Wormia to the genus thus formed because the last
name dates from 1783 while Capellia dates from 1825.  –  In case of union of the two genera
Cardamine and Dentaria, which were founded at the same time by Linnaeus (Sp. pl. ed. 1, 653
and 654 [1753]; Gen. Pl. ed. 5, n. 726, 727) the collective genus must be called Cardamine because
that name was chosen by Crantz (Class. Crucif., 126 [1769], who was the first to suggest the
union.  –  H. Hallier (in Engl. Bot. Jahrb. XVIII, 123) united the three species of Ipomoea, I. verticillata
Forsk. (1775), I. rumicifolia Choisy (1834) and I. Perrottetii Choisy (1845); the species is still called
I. verticillata Forsk. as Forskal’s name is the earliest.
 –  Swartz (Prodr. 16) described two species
of Piper, P. glabellum and P. scandens which he subsequently (Fl. Ind. Occ. i. 68) regarded as con-
specific, choosing the name P. glabellum, this name therefore and not P. scandens must be used for
the combination.


                XXVI.   Authors who have to choose between two generic names should note the following

                1 Of two names of the same date to prefer the one which was first accompanied by the
description of a species.

                2 Of two names of the same date, both accompanied by descriptions of species, to prefer
the one, which, when the author made his choice, included the larger number of species.

                3 In cases of equality from these various points of view to prefer the more correct and
appropriate name.

                XXVII.   When several genera are united as subgenera or sections under one generic
name, that subdivision which was first distinguished or described may retain its name (ex.: Anar-
sect. Anarrhinum; Hemigenia sect. Hemigenia), or be preceded by a prefix (Anthriscus sect.
Eu-Anthriscus) or followed by a suffix (Stachys sect. Stachyotypus).  These prefixes or suffixes lapse
when the subdivisions are raised to generic rank.

                XXVIII.   When several species are united as subspecies or varieties under a collective
name, that subdivision which was first distinguished or described may retain its name (ex.: Saxifraga
subsp. aspera) or bear a prefix (Alchemilla alpina subsp. eu-alpina) or be designated by some
customary title (normalis, genuinus, typicus, originarius, verus, veridicus etc.).  These prefixes or
terms lapse when the subdivisions are raised to specific rank.

                Art. 47 When a species or subdivision of a species is divided into two
or more groups of the same nature, if one of the two forms was distinguished or
described earlier than the other, the name is retained for that form.

                Examples.  –  Genista horrida DC. Fl. Franc. IV. 500 was divided by Spach (in Ann. Sci.
ser. 3, II., 253 [1844]) into three species: G. horrida DC., G.Boissieri Spach and G. Webbii
Spach; the name G. horrida was rightly kept for the earliest described form, that described and


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figured by Vahl and Gilibert.  –  Several species (Primula cashmiriana Munro, P. erosa Wall.) have
been separated from Primula denticulata Sm. (Exot. Bot. II, 109, tab. 114), but the name P. denticulata
has been rightly kept for the form which Smith described and figured under this name.

                Art. 48 When a subgenus or section or species is moved into another
genus, when a variety or other division of a species is moved into another species,
retaining there the same rank, the original name of the subgenus or section, the first
specific epithet, or the original name of the division of the species must be retained
or must be re-established, unless, in the new position there exists one of the obstacles
indicated in the articles of section 7.

                Examples.  –  The subgenus Alfredia Less. (Syn. p. 6, 1832) of the genus Rhaponticum
keeps its name when placed in the genus Carduus: Carduus sect. Alfredia Benth. et Hook. fil.; the
section Vaccaria DC. of the genus Saponaria keeps its name when placed in the genus Gypsophila:
Gypsophila sect. Vaccaria Gren. et Godr.  –  Lotus siliquosus L. Syst. ed. 10. p. 1178 (1759) when
transferred to the genus Tetragonolobus must be called Tetragonolobus siliquosus Roth Tent. Fl. germ.
I. 323 (1788) and not Tetragonolobus Scandalida Scop. Fl. Cam. ed. 2, II, 87 (1772).  –  Betula incana
L. Suppl. p. 417 (1781) when transferred to the genus Alnus must be called Alnus incana Willd.
Sp. Pl. IV, 335 (1805), not Alnus lanuginosa Gilib. Exerc. Phytol. II, 402 (1792).  –  Satyrium nigrum
L. Sp. Pl. ed. 1, 944 (1753), when placed in the genus Nigritella must be called Nigritella nigra
Reichb. f. Ic. Fl. Germ. et Helv. XIV, 102 (1851), not Nigritella angustifolia Rich. in Mém. Mus.
IV, 56 (1818).  –  The variety γ micranthum Gren. et Godr. (Fl. France, I, 171 [1847]) of
Helianthemum italicum Pers., when transferred as a variety to H. penicillatum Thib. retains its name:
H. penicillatum var. α micranthum Grosser (in Engl. Pflanzenreich, Heft 14, p. 115 [1903]).  –  The
variety subcarnosa Hook. fil. (Bot. Antarct. Voy. I, 5 [1847]) of Cardamine hirsuta L., when trans-
ferred as a variety to C. glacialis DC., retains its name: C. glacialis var. subcarnosa O. E. Schulz
(in Engl. Bot. Jahrb. XXXII, 542 [1903]); the citation of an earlier synonym (Cardamine propinqua
Carmichael in Trans. Linn. Soc. XII, 507 [1818]) has no influence on the choice of the name of
the variety (see art. 49).  In all these cases, older but incorrect combinations must give place to
more recent combinations in which the rule has been observed.

                Art. 49 When a tribe becomes a family, a subgenus or a section becomes
a genus, a subdivision of a species becomes a species, or the reverse of these changes
takes place, and speaking generally when a group changes its rank, the earliest name
(or combination of names) received by the group in its new position must be regarded
as valid, if it is in conformity with the rules, unless there exist any of the obstacles
indicated in the articles of section 7.

                Examples.  –  The section Campanopsis R. Br. Prodr. Fl. Nov. Holl., 561 (1810) of the
genus Campanula, was first raised to generic rank by Schrader, and must be called Wahlenbergia

Schrad. Cat. Hort. Goett. (1814) not Campanopsis O. Kuntze Rev. Gen. II, 378 (1891).  –  Magnolia
L. var. foetida L. Sp. pl. ed. 1, p. 536 (1753), raised to specific rank, must be called Mag-
nolia grandiflora
L. Syst. Nat. ed. 10, 1082 (1759) not Magnolia foetida Sarg. in Gard. and For.
II, 615 (1889).  –  Mentha spicata L. var. viridis L. Sp. pl., ed. 1, 576 (1753) was raised to the
rank of a species by Hudson, and must be called Mentha spicata Huds. Fl. angl. ed. 1, p. 221
(1762) not Mentha viridis L. Sp. pl., ed. 2, 804 (1763).  –  Lythrum intermedium Ledeb. (Ind. Hort.
[1822]), regarded as a variety of L. Salicaria L., must be called L. Salicaria var. gracilis Turcz.
(in Bull. Soc. Nat. Moscou, XVII, 235 [1844]), not L. Salicaria var. intermedium Koehne (in Engl.
Bot. Jahrb. I, 327 [1881]).  In all these cases names which are in accordance with the old law of
Alphonse de Candolle must give place to older names and combinations.


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                Recommendations.   Authors who make the changes discussed in article 49 should note
the following recommendations in order to avoid a change of name in case of a change of rank:

                XXIX.   1º.  When a sub-tribe becomes a tribe, when a tribe becomes a subfamily, when
a subfamily becomes a family, etc., or when the inverse changes occur, do not alter the root of a
name but only the termination (-inae, -eae, -oideae, -aceae, -ineae, -ales, etc.), unless, in the new position,
one of the obstacles indicated in the articles of section 7, supervenes, or the new designation becomes
a source of error, or there is some other serious reason against it.

                2º.  When a section or a subgenus becomes a genus, or the inverse changes take place,
retain the old names, unless this results in two genera of plants having the same name, or the
existence of two subdivisions of the same name in the same genus, or one of the obstacles indicated
in the articles of section 7 supervenes.

                3º.  When a subdivision of a species becomes a species or the inverse change occurs, retain
the original epithets, unless this results in two species bearing the same name in the same genus, or
two subdivisions bearing the same name in the same species, or unless any of the obstacles indicated
in section 7 supervenes.

                Art. 49bis Among Fungi with a pleomorphic life-cycle the different successive
states of the same species (anamorphoses, status) can bear only one generic and
specific name (binomial) that is the earliest which has been given, starting from Fries,
Systema, or Persoon, Synopsis, to the state containing the form which it has been
agreed to call the perfect form, provided that the name is otherwise in conformity
with the rules.  The perfect state is that which ends in the ascus stage in the Asco-
mycetes, in the basidium in the Basidiomycetes, in the teleutospore or its equivalent
in the Uredinales, and in the spore in the Ustilaginales.

                Generic and specific names given to other states have only a temporary
value.  They cannot replace a generic name already existing and applying to one or
more species, any one of which contains the “perfect“ form.

                The nomenclature of Fungi which have not a pleomorphic life-cycle follows
the ordinary rules.

                Examples.  –  The names Aecidium Pers., Caeoma Link and Uredo Pers. designate different
states (aecidiosporic with or without pseudoperidium, uredosporic) in the group Uredinales.  The generic
name Melampsora Cast. [Obs. II, 18 (1843)], applied to a genus which is defined by means of the
teleutospores, cannot therefore be replaced by the name Uredo Pers. [in Römer Neu. Mag. I, 93
(1794)] since the name Uredo is already used to designate a state.  –  Among the Dothideaceae
(Ascomycetes) a species of the genus Phyllachora Nitschke, P. Trifolii (Pers.) Fuck. Symb. 217
1869–70) has an older synonym, Polythrincium Trifolii G. Kunze Myk. Heft. I, 13, t. 1 f. 8 (1817)
based on the conidial state of this species.  The name Polythrincium cannot displace that of Phyllachora
because it represents an inferior state.  –  The name Phoma Fries emend. Desm. has been given to a
group of Fungi Imperfecti (Deuteromycetes), several members of which have beenrecognised as the
spermogonial state of species of the genus Diaporthe (Valsaceae, Ascomycetes): thus Phoma Ailanthi
Sacc. belongs to Diaporthe Ailanthi Sacc., Phoma alnea (Nitschke) Sacc. to Diaporthe alnea Fuck.,
Phoma detrusa (Fries) Fuck. to Diaporthe detrusa Sacc. etc.  But the perfect state of many species
of the ‘genus’ Phoma is not known and in some cases probably does not exist.  Hence the practical
necessity for retaining the name Phoma to designate the group of Fungi Imperfecti in question.

Section 7.   On names that are to be rejected, changed or modified.

                Art. 50 No one is authorised to reject, change or modify a name (or com-
bination of names) because it is badly chosen, or disagreeable, or another is pre-
ferable or better known, or because of the existence of an earlier homonym which


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is universally regarded as non-valid, or for any other motive either contestable or of
little import. (See also art. 57.)

                Examples.  –  This rule was broken by the change of Staphylea to Staphylis, Tamus to Thamnos,
Mentha to Minthe, Tillaea to Tillia, Vincetoxicum to Alexitoxicon; and by the change of Orobanche
to O. sarothamnophyta, O. Columbariae to O. columbarihaerens, O. Artemisiae to O. artemisi-
.  All these modifications (which are contrary to Art. 50) must be rejected.  –  The name
Diplomorpha Meissn. in Regensb. Denkschr. III, 289 (1841) must not be substituted for the generic
name Wickstroemia Endl. Prodr. fl. Norfolk., 47 (1833) because of the earlier homonyms Wi(c)k-
Schrad. Goett. gel. Anz., 710 (1821) and Wi(c)kstroemia Spreng. in Vet. Akad. Handl.
1821, 167, t. 3, for the former is merely a synonym of the genus Laplacea Kunth (1821)
and the latter of a subdivision of the genus Eupatorium L. (1753).

                Recommendations.   See on the subject of homonyms recommendations V b and XIV f
which suggest that cases of this kind should be avoided for the future.

                Art. 51 Everyone should refuse to admit a name in the following cases:

                1. When the name is applied in the plant kingdom to a group which has
an earlier valid name.

                2. When it duplicates the name of a class, order, family or genus, or a sub-
division or species of the same genus, or a subdivision of the same species.

                3. When it is based on a monstrosity.

                4. When the group which it designates embraces elements altogether in-
coherent, or when it becomes a permanent source of confusion or error.

                5. When it is contrary to the rules of sections 4 and 6.

                Examples.  –  1°. Carelia Adans. (1763) is a name which was applied by its author to a genus
which had already received a valid name (Ageratum L. [1753]) (synonym); similarly Trichilia alata
N. E. Brown (in Kew Bull. 1896, 160) is a name which cannot be maintained because it is a

synonym of T. pterophylla C. DC. (in Bull. Herb. Boiss. II, 581 [1894]).  –  2°. Tapeinanthus, a name
given by Boissier to a genus of Labiatae was replaced by Thuspeinanta by Th. Durand, because
of the existence of an earlier and valid genus, Tapeinanthus Herb. among the Amaryllidaceae;

(homonym).  Similarly Astragalus rhizanthus Boiss. (Diagn. Pl. Or. ser. 1, II, 83 [1843]) was renamed
A. cariensis Boiss. because of the existence of an earlier valid homonym, Astragalus rhizanthus Royle

Illustr. Bot. Himal. p. 200 (1835).  –  4º. The genus Uropedium Lindl. was based on a monstrosity

which is now referred to Phragmopedilum caudatum Rolfe.  –  5°. The genus Schrebera L. derives its
characters from the two genera Cuscuta and Myrica (parasite and host) and must be dropped; and
the same applies to Lemairea De Vr. which is made up of elements taken from different families.

Linnaeus described under the name of Rosa villosa a plant which has been referred to several diffe-
rent species and of which certain identification seems impossible; to avoid the confusion which results
from the use of the name Rosa villosa, it is preferable in this case, as in other analogous cases, to
abandon the name altogether.

                Art. 52 The name of an order, suborder, family or subfamily, tribe or sub‐
tribe, must be changed when it is taken from a genus which, by general consent,
does not belong to the group in question.

                Examples.  –  If it were to be shown that the genus Portulaca does not belong to the family
Portulacaceae, the name Portulacaceae would have to be changed.  –  Nees (in Hooker and Arnott,
Bot. Beechey’s Voy. 237 [1836]) gave the name Tristegineae to a tribe of Gramineae, after the genus
Tristegis Nees (a synonym of the genus Melinis Beauv.).  But Melinis (Tristegis) having been excluded
from this tribe by Stapf (in Fl. Cap. VII, 313) and by Hackel (in Oesterr. bot. Zeitschr. LI, 464),
these authors have adopted the name Arundinelleae from the genus Arundinella.


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                Art. 53 When a subgenus, a section or a subsection, passes as such into
another genus, the name must be changed if there is already, in that genus, a valid
group of the same rank, under the same name.

                When a species is moved from one genus into another, its specific epithet
must be changed if it is already borne by a valid species of that genus.  Similarly
when a subspecies, a variety, or some other subdivision of a species is placed under
another species, its name must be changed if borne already by a valid form of like
rank in that species.

                Examples.  –  Spartium biflorum Desf. (1798–1800) when transferred by Spach in 1849 to
the genus Cytisus could not be called Cytisus biflorus, but was renamed Cytisus Fontanesii; because
of the previous existence of a valid species Cytisus biflorus L’Hérit. (1789).  The earliest synonym
of Calochortus Nuttallii Torr. et Gray (in Pacific Rail. Rep. II, 124 [1855–1856]) is Fritillaria alba
Nutt. (Gen. Amer. I, 222 [1818]) but we cannot restore the original epithet of this species, although
this has been done in the Notizbl. des K. bot. Gartens und Mus. Berl. II, 318 (1899), because there
exists already a valid species in the genus with the name Calochortus albus Dougl. in Maund
Botanist t. 98 (1839).

                Art. 54 Names of genera must be rejected in the following special cases:

                1 When they coincide with a technical term concurrently used in morphology,
unless they are accompanied by specific names.

                2 When they express uninominal nomenclature.

                3 When they are formed of two words, unless these two words were from
the first united or joined by a hyphen.

                Examples.  –  1º. Generic names such as Lignum, Radix, Spina, Radicula etc. would not now be
admissible; on the other hand a generic name like Tuber should not be rejected when it has been published

with specific names (Tuber cibarium etc.).  –  2º. Ehrhart (Phytophylacium [1780] and Beiträg. IV,
145–150) made use of a uninominal nomenclature for species known at that time under binary
names (Phaeocephalum, Leptostachys, etc.).  These names, which resemble generic names, must not be
confused with such and are to be rejected, unless a subsequent author has given them the value of
a generic name: for example Baeothryon, a uninominal expression of Ehrhart’s, has been applied to
a genus characterised by A. Dietrich Spec. Pl. II, 89 (1833).  –  3º. Names like Quisqualis (a single
word from the first), Sebastiano-Schaueria and Neves-Armondia will stand.

                Art. 55 Specific names must also be rejected in the following special cases:

                1º.  When they are ordinals serving for purpose of enumeration.

                2º.  When they merely repeat the generic name.

                Examples.  –  1º. Boletus vicesimus sextus, Agaricus octogesimus nonus.  –  2º. Linaria Linaria,
Raphanistrum Raphanistrum etc.

                Art. 56 In the cases foreseen in articles 51 to 56, the name to be rejected
or changed is replaced by the oldest valid name in the group in question, and in
default of such one a new name (or new binomial) must be made.

                By valid name is implied a name, and especially a combination of names
formed in accordance with the rules of nomenclature.  The author of a new combi-
nation may, if he wish, borrow the specific epithet from an older non-valid binomial
(still-born name) or make use of a new one.

                Examples.  –  Linum Radiola L. (1753) when placed in the genus Radiola must be called
Radiola linoides Roth (1788); the earlier synonym Linum multiflorum Lamk. (1778) cannot be con-


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sidered as this combination is contrary to art. 51, 1º of the Rules.  –  Peucedanum Silaus L. (1753)
when placed in the genus Silaus must be called Silaus flavescens Bernh. (1800); the earlier synonym
Seseli selinoides Jacq. (1762) cannot be considered as this combination is contrary to art. 48 of the
Rules.  –  Polypodium montanum Vogl. (1781) non Lamk (1778) = P. Oreopteris Ehrh. ex Willd.
(1789), when placed in the genus Dryopteris must be called D. Oreopteris Max.; the earlier synonym
Polypodium montanum Vogl. cannot be considered as this combination is contrary to the Rules
art. 51, 2º.  It is true that P. montanum Lamk has been transferred later to the genus Cystopteris
[C. montana (Lamk) Desv.] but the genus Cystopteris dates only from the year 1806; Ehrhart could
therefore neither forsee nor take account of it.  –  See also the examples cited under articles 51 and 53.

                Art. 57 The original spelling of a name must be retained, except in case
of a typographic or orthographic error.  When the difference between two names,
especially two generic names, lies in the termination, these names are to be regarded
as distinct even though differing by one letter only.

                Examples: Rubia and Rubus, Monochaete and Monochaetum, Pepoma and Peponium, Iria and Iris.


                XXX.   The liberty of making orthographic corrections must be used with reserve, especially
if the change affects the first syllable, and above all the first letter of a name.

                XXXI.   Many names differ by a single letter without risk of confusion (ex. Durvillea and
Urvillea).  In cases where a close approach to identity is a source of error (ex. Astrostemma and
Asterostemma in one and the same family, Asclepiadaceae, Pleuripetalum and Pleuropetalum in Or-
) only one, the older, of the names should be kept, in accordance with article 51, 4°.


Chapter IV.   Modification of the rules of botanical nomenclature.

                Art. 58 The rules of botanical nomenclature can only be modified by com‐
petent persons at an international Congress convened for the express purpose.

Appendix.   Various recommendations.

                XXXII.   Botanists should use in modern languages latin scientific names or those immediately
derived from them, preferably to names of another kind or origin.  They should avoid the use of
the latter unless these are very clear and in common use.

                XXXIII.   Every friend of science should oppose the introduction into a modern language
of names of plants which are not already there, unless they are derived from latin botanical names
by means of some slight alteration.

                XXXIV.   The metric system only is used in botany for reckoning weights and measures.
The foot, inch, line, pound, ounce etc. should be rigorously excluded from scientific language.

                Altitude, depth, rapidity etc. are measured in metres.  Fathoms, knots, miles etc. are ex-
pressions which should disappear from scientific language.

                XXXV.   Very minute dimensions are reckoned in μ (micromillimetres, microns, or thou-
sandths of a millimetre) and not in fractions of a millimetre or line etc.; fractions encumbered with
ciphers and commas are more likely to give rise to mistakes.

                XXXVI.   Authors are asked to indicate clearly and precisely the scale of the figures
which they publish.

                XXXVII.   Temperatures are expressed in degrees of the centigrade thermometer of Celsius.

                XXXVIII.   It is of the utmost importance that the original specimens on which are based
the descriptions of new groups should be preserved.  In the case of microscopic Cryptogams, the
preparations and original drawings should be preserved; and in the case of fleshy fungi, watercolour
sketches and specimens suitably prepared or dried, etc.



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