EDITOR'S PREFACE. xxv 



ness, the shape of leaves, or indeed anything short of a va- 

 riation in the parts connected with the reproductive organs, 

 may be regarded as falling within the limits of those changes 

 which are induceable by climate. 



It may be somewhat encouraging to the readers of this 

 little Volume, when they are rising from its perusal bewil- 

 dered by the contemplation of the vast fecundity of Nature, 

 spread before them in the pictures of the vegetation of dif- 

 ferent climes therein given, to find that the efforts of many 

 distinguished botanists in the present day are directed rather 

 to the task of reducing the number of recognized species, 

 than of increasing it. 



But, it may be asked, if these principles be admitted, 

 where are we to stop ? and why may we not proceed, in the 

 spirit of the author of a well-known Work, to deny the ex- 

 istence of species altogether, except perhaps as steps or halt- 

 ing places in that supposed march of progression, by which 

 the most elaborately organized plant is gradually educed 

 by a process of successive transmutations from the most 

 simple one, just as in the animal kingdom the most perfect 

 mammal is from the monad ? 



Without entering fully into this grave question, upon 

 which much ink has lately been spilt, sometimes mingled, 



