460 Ill. SEGREGATES ETC. 
In general, however, the differences between our describing books 
turn more frequently on the greater or less number of segregate 
species which are taken up by them. And where this only has 
been the case, without such injudicious transfers of name from one 
plant to another, or from one combination to a different com- 
bination, the recorded localities can be made available so long as 
we are keeping to the larger aggregates. But nothing is gained 
in this way, towards ascertaining the special distribution of the 
segregates. For this latter purpose the requirements are different 
and more rigid. The subordinate forms, whether held to be 
species or varieties, need to be clearly discriminated; they must 
be mentioned by names which tell precisely what is meant, and 
nothing else; and whenever possible it should be stated whether 
only the one special form is found in the locality, or other forms 
also. So little hitherto has been done in this way for many of the 
segregate forms, that their treatment in the following pages can be 
only a meagre beginning. 
How far to notice the more petty segregates, usually the more 
difficult to trace topographically, is a matter of some hesitation. 
Where it is practicable to do so, I am inclined to notice even 
petty segregates. But some limit must be set to this; and in 
general mere differences of size, or colour, or pubescence, will not 
be deemed sufficient to warrant separate treatment; even though 
such differences are made into specific distinctions by some 
botanical describers. In the old writers, of ante-Linnean times, 
the white-flowered varieties were not seldom taken up as species. 
And at the present time we find rather a tendency to make 
varieties “ minor,” different only by size from the typical forms. 
The absolute difference between “ glabra” and “hirsuta” may be 
allowed usually to constitute good varieties; but that of a 
graduated pubescence, a little more or a little less, will be held 
insufficient distinction, 
