36 SCIENTIFIC WOEK, 1860-1865 



from the same, beside which the fossil plants are as nothing, 

 in point of absolute value of characters for systematic 

 determination. I am as always impressed with the identity 

 of physical features and wonderful analogy of biological 

 between Alps and Himalayas, the former we can suppose we 

 understand, because physical causes are the same everywhere 

 and the sequence of these is probably the same in Alps and 

 India: The representation of allied species too we can now 

 (thanks to you) account for largely, but the repetition of 

 forms in plants and animals in no way allied is always a 

 puzzle, especially when accompanied by startling contrasts 

 between allied forms. These latter can best no doubt be 

 accounted for by the indirect action of physical causes (i.e. 

 Nat. Selection) and I think there are already many reliable 

 facts to be- quoted in illustration of this, and that after the 

 course of alteratives you have administered I could write 

 a suggestive chapter, comparing the vegetation of Alps, 

 Andes and Himalayas in my (never to be begun) book on 

 Plants. 



. I cannot yet give up my dream of meeting you in Switzer- 

 land one day ; if you ever did come here, and I could see you 

 for 5 minutes a day, I should be the happiest man alive. 

 These rocks, plants and insects teem with thoughts of you 

 and reminiscences of your writings. 



Your Orchid book, which I have not read through, has 

 suggested to me that insects &c. may have a wonderful deal 

 more to do with checking migration than climate or geo- 

 graphies, and that the absence of whole genera may thus one 

 day be accounted for by absence of genera of insects : in 

 short that the Cat and Clover story is capable of immediate 

 expansion by any one having sufficient knowledge of Plants, 

 Insects and Geography. 



Thursday, July (24 ? ) 1862. 



I was delighted with Heer, and went over all his collections, 

 which are grand and good ; they serve to convince me that 

 the Miocene vegetation was Himalayan, not American as H. 

 supposed. Heer's error was very natural, for no one knows 

 from any published works what the real nature of the 

 Himalayan vegetation^is: 



Darwin's answer to the following is given in M.L. i. 197. 



