!27 



INTRODUCTION 



TO 



THE FLORA. 



Our knowledge in detail of the character and mode of 

 operation of the agencies which have been employed to bring 

 about the distribution of plants and animals over the surface of 

 the earth, and thus to produce the condition of things which at 

 the present time we behold, is very limited indeed. A\'hich arc 

 true species, which aboriginally distinct, and which mere modi- 

 fications of one common stock produced by the influence of 

 mere change of circumstance, this point it is impossible for us 

 to determine with certainty with regard to what appear to us 

 now as truly distinct species, and are described as such in our 

 handbooks. We cannot sail backward along the stream of time, 

 and unravel the intricacies of their bygone genealogies. We 

 are obliged, for practical purposes, to take them as we find 

 them ; to describe or receive as species all those associations of 

 an indefinite number of plants and animals which wc observe 

 to possess in common what we agree to consider sufficiently 

 well-marked permanent characteristics ; the difference between 

 the so-called analysts and synthcsists of descriptive zoology and 

 botany really amounting to no more than this, that whilst both 

 are agreed in the theoretic idea that the individuals of a species 

 should possess permanent characteristics in common, yet when 

 it comes to the carrying out of the idea into practice, the latter 

 insist upon more decidedly marked diagnostic characters, that 

 is to say, upon broader lines of demarcation, than the former. 

 And hence arises the (l\ct, that species as described in books 

 are often combinations of very unequal value, and that, especially 



pot. Trans, V.N.U., Vol. 3, 



