INTRODUCTION. lxv 



liar appendage of the embryo, or rather for a particular form of the radi- 

 cle, — an hypothesis which that distinguished botanist supported with great 

 skill, but which is now generally abandoned. 



I have now gone through the whole of the characters of which bota- 

 nists make use in distinguishing and determining the affinities of plants, 

 and I think it must be apparent that the difficulties connected with the sub- 

 ject are neither slight nor easily to be overcome. If these observations are 

 properly attended to, no one can be at a loss to understand, that to define 

 any group of plants, of what rank soever, is impracticable; that differ- 

 ences of structure are of an uncertain and unequal value ; and that the 

 affinities of plants are never to be absolutely made out by solitary charac- 

 ters, but depend upon more or less intricate combinations, the power of 

 judging of which, is the same test of a skilful botanist, as an appreciation 

 of symptoms is that of a physician. 



