PRELIMINARY REMARKS. 
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HE Tyro is no doubt often surprised at finding his botanical 
mentors differing so widely among themselves in their estimate 
of the number of species contained in the British Flora; this 
difference is, however, more apparent than real, and arises from 
the various ways in which the term species is understood. In 
those cases where authors do not agree respecting the number of 
species contained in a genus, they would probably all admit the 
existence of the same number of groups or forms, more or less 
separable and definable by characters; but some do not consider 
that all of these groups deserve to be called species, while others 
give that title to every one of them. This variety of opinion will 
be found to prevail most in the Floras of districts which have 
been most carefully examined. It is not until the plants have 
received very minute attention that the less obviously distinct 
forms will be brought into notice. A good exemplification of 
this is to be seen in the daily-increasing divergence of opinion 
between two different classes of botanists as to the number of 
species contained in the well-examined Floras of Great Britain, 
France, Germany, and Belgium. 
It ‘will really be found that in many genera individual plants 
may be grouped into more restricted assemblages than species 
(taking the term in its widest acceptation), and that these 
subordinate groups bear to species somewhat the same relation 
that species themselves do to genera. To such the name of sub- 
species or races may be given. 
