For the present, then, and possibly for ages to come, the 
Botanist must depend upon other principles in his distine- 
tion of plants into species: he must apply such experience 
as he may be able to derive from those species with 
the variations of which he is certainly acquainted, to those 
- of which he can have no certain knowledge, except by way 
of inference; and in the total absence of all demonstrative 
evidence, he must trust to what may be called the evidence 
of induction. It is obvious that this kind of evidence is 
vague in the greatest possible degree; that it is unsatis- 
factory, and incapable of either direct or circumstantial 
proof; and that, in truth, its value will be estimated very 
differently by different persons. In practice it leads to two 
opposite methods of arrangement ; firstly, to combining all 
plants having a particular degree of relationship, upon the 
assumption, that if certain plants differing in a particular 
manner are known to be one natural species, therefore all 
plants with the same kind of differences are also of one 
species; secondly, to distinguishing plants by very slight 
differences, upon the ground, that till we really know some- 
thing positive respecting them, it is more conducive to the 
ends of science to distinguish than to combine, and perhaps 
confound. ‘To us, both these plans are objectionable. We 
would neither combine too strictly upon uncertain evidence, 
neither would we distinguish too minutely ; but whenever 
we possessed information, the accuracy of which could not 
be doubted, we would then strictly circumscribe our species 
within the limits of the definition previously referred to. 
For example, there is no question as to the naturally spe- 
cific identity of all British roses, except R. canina and 
R. arvensis; of nearly all the Amaryllises comprehended 
by Mr. Herbert under the name of Hippeastrum; of the 
ereater number of Crinums; and of most of the modern 
species of Aconitum and Pelargonium: but there does not 
yet exist any evidence equally satisfactory of the identity 
of the supposed species of /sculus, Ribes, Pyrus, Prunus, 
Crategus, or Ulmus; or, indeed, of the greater part of the 
most remarkable plants domesticated in our gardens. In 
this uncertainty, we would proceed with moderation; on 
the one hand distinguishing, from want of information, what 
our more accurately informed successors may combine ; and 
on the other hand combining such plants as our prede- 
cessors, from the same want of sufficient experience, have 
distinguished. Vo AV 
