XVI 
INTRODUCTION 
the original trivial name when a species has been reduced to varietal rank, even when a varietal 
name was already in existence. This practice is condemned by the rules. 
Names of hybrids 
In the case of hybrids, the rule is that the hybrid in question shall be designated by the names 
of its parents (or putative parents), the latter names being placed in alphabetical order and con- 
nected by a cross. Thus, if it is known or believed that a given plant has been produced by the 
crossing of Salix caprea and S. viminalis , the hybrid is designated .S'. caprea x viminalis ; and this 
rule holds no matter how many species are known or supposed to have taken part in the production 
of the hybrid. The connecting of the trivial names by a cross is rather a new plan. Formerly, 
a hyphen was often used instead ; and at that time it was not the rule to place the trivial names 
in alphabetical order. Hence, we often see in the older books such names as Salix caprea- 
viminalis and S. viminalis-caprea . Sometimes, instead of a cross or a hyphen, a connecting 
letter was used, as in Polygonum minori-persicaria. We do not regard these conventional signs or 
connectives as of any importance ; and accordingly, in the present work, we cite, as the first 
authority of a hybrid-plant, the first authority who so combined the correct trivial names as to show 
that he regarded the plant as being of hybrid origin ; and we deliberately change his conventional 
sign when this is different from the one adopted nowadays. 
By the rules of nomenclature, botanists are allowed, if they wish, to bestow upon a hybrid a 
quasi-binominal, i.e., a binominal with a cross placed in front of it. Thus, a hybrid has been recently 
named Helianthemum chamaecistus x marifolium ( x H. bickhami). This means that the hybrid in 
question may be named either H. chamaecistus x marifolium or x H. bickhami, as is preferred. In 
the present work, the former of these two methods is employed ; and quasi-binom'ma\s are reserved for 
subdivisions of hybrid plants. In general, we do not think it desirable to give quasi- binominals to 
hybrid-forms ; but there are a few exceptional cases where the desirability exists. For example, it is 
desirable to give such names to putative hybrids when these have either a commercial or artistic 
value, as in the case of the Huntingdon elm ( x U. vegeta). Again, when a hybrid-form has been 
produced artificially and when therefore its precise origin is known, it is sometimes well to describe 
it and to reserve a special name for it. 
It is, however, inadmissible to cite as the author of a hybrid-form (or putative hybrid-form) 
the name of an author who described the same plant as a species or variety. To do so, in fact, 
would in many cases do the author in question grave wrong. For example, Sir J. E. Smith named 
as species a large number of willows which are now regarded as hybrids ; but Smith combated, and 
combated most strongly with what were almost his dying words, the view that his species of Salix 
were largely hybrids. If therefore Smith’s species in this genus are reduced to hybrids, some authority 
other than Smith must be found for the hybrids in question ; and this authority is the botanist who 
first reduced the plant from specific rank to hybrid rank. 
Latin diagnoses 
Article 36 states that on and after January 1st, 1908, the publication of a new group of recent plants 
will be valid only when it is accompanied by a Latin diagnosis. Whilst generally adhering to this rule, 
we do not think it is necessary to insist on it in the cases of series, subseries, subvarieties, formae , and 
hybrids. 
Size of species 
It is necessary to make clear our position with regard to the size of the species adopted in 
the present work. In a general way, there are three possible plans from which an author of 
a flora must make his choice. It is almost needless to state here that each plan has its ad- 
herents and its advocates. First, there is the plan of using comprehensive species. This plan 
is usually chosen, and very naturally chosen, by botanists who attempt to write the flora of a 
large and a comparatively unknown country ; and it is also the plan usually adopted by botanists 
who write monographs of the larger groups of plants. Secondly, there is the plan of using very 
small species. This plan has from time to time been adopted by botanists who intensively study 
the flora of a limited district or a small group of plants. The British botanist Bentham may be 
cited as a type of botanist who used very large species, and the French botanist Jordan as a type 
of one whose species were very small. 
