XIV 
INTRODUCTION 
Genera , subgenera , sections , and subsections 
The names of genera, subgenera, sections, and subsections are either substantives or are 
adjectives used as substantives. These names, and also all names of groups of lower rank except 
series and subseries, are used in the singular and may be of any gender, whilst the names of 
all groups of higher rank are in the plural and are feminine. 
Seines and subseries 
The names of series and subseries are the names of a species in the particular series <3r 
subseries, the name of the species being put in the plural and its gender retained. The species 
chosen must be the species with the oldest trivial name, or one of the oldest when two or 
more are of the same age. The names of series and subseries differ from the names of higher 
groups, and resemble trivial and varietal names, in that they may be used repeatedly in different 
genera. 
Species 
The name of a species consists of a generic name (the name of the genus in which the 
species is placed) and a trivial name. The resulting binominal is the specific name. 
The trivial name is usually an adjective agreeing in gender with the generic name. It may 
also be a substantive either in the genitive or used in apposition. Sometimes it is the name 
of a genus, old (pre-Linnaean) or new (post-Linnaean). When it commemorates some person or 
place or habitat, it may be a substantive used in the genitive or it may be adjectival in form. 
A trivial name used per se is virtually meaningless, as it is indistinguishable from a name 
similarly used of a subspecies, race, variety, subvariety, or forma. Similarly, trinominals (e.g., Salix 
cinerea aquatica ) are ambiguous, as it is not known whether the plants so designated are to be 
regarded as subspecies, races, varieties, subvarieties, or formae. 
“ The Kew rule ” 
The general rule of nomenclature previously laid down becomes very important when applied 
to the trivial names of species. Before the ruling of the Vienna congress in 1905, it was usual in 
the British empire and in France to adopt what is sometimes known as “the Kew rule.” This 
rule states that the valid trivial name is the earliest one which a species had received when it 
was placed in its correct genus ; and this rule was adopted by Dr B. Daydon Jackson in the Index 
Kewensis. Fortunately or unfortunately, “the Kew rule” is now obsolete. 
“ The Berlin rule ” 
A rule which, for the sake of brevity, may be referred to as “ the Berlin rule ” was, for a 
time at least, used by the Berlin school of systematists. The rule states that a trivial name 
which had been in general use for 50 years should be regarded as fixed, no matter whether 
or not an older trivial name existed. We confess to having a great deal of sympathy with this 
position, although there are objections to it. For example, it often happens that a certain 
name of a given species obtains in a certain coterie or school of botanists, whilst another name 
for the same species obtains in another coterie or school. Naturally, each coterie or school wishes 
to preserve the name with which it is most familiar. 
“ The Vienna rule" 
To obviate this difficulty, the international congress of botanists held at Vienna in 1905 
decided that the trivial to be adopted is the earliest one which the species had received. 
There are objections to this as to any other rule which might be framed bearing on the matter, 
not the least of which is the unfortunate necessity of occasionally having to discard a well-known 
trivial name for an obscure one ; but the rule is now international and therefore more authoritative 
than any other. 
