202 Darwin, and after Darwin. 



belong to several distinct orders, and that they are adapted to 

 widely different stations, it can hardly be supposed that their 

 differences are of any special service to them in the New and 

 Old worlds ; and, if so, such differences cannot have been gained 

 through natural selection, and must be attributed to the long 

 continued action of a different climate '." 



These cases, however, I quote mainly in order to 

 show Darwin's opinion upon the matter, with reference 

 to the absence of natural selection. For, where the 

 vegetable kingdom is concerned, the fact of climatic, 

 variation is so general, and in its relation to diag- 

 nostic work so important, that it constitutes one of 

 the chief difficulties against which species-makers 

 have to contend. And the more carefully the subject 

 is examined the greater does the difficulty become. 

 But, as to this and other general facts, it will be 

 best to allow a recognized authority to speak; and 

 therefore I will give a few extracts from Kerner's 

 work on Gute und schlechte Arten. 



He begins by showing that geographical (or it 

 may be topographical) varieties of species are often 

 so divergent, that without a knowledge of intermediate 

 forms there could be no question as to their being 

 good species. As a result of his own researches on 

 the subject, he can scarcely find language strong 

 enough to express his estimate of the extent and 

 the generality of this source of error. In different 

 parts of Europe, or even in different parts of the 

 Alps, he has found these climatic varieties in such 

 multitudes and in such high degrees both of con- 

 stancy and divergence, that, after detailing his results, 



' Variation, &c. vol. ii, p. 371. 



