43 8 GEOGRAPHICAL DISTRIBUTION [Chap. VI 



Letter 333 further south if nut opposed "]. Still I must confess that 

 all your arguments pro may be much stronger put than 

 you have. 



I am more reconciled to iceberg transport than I was, 

 the more especially as I will give you any length of time 

 to keep vitality in ice, and, more than that, will let you 

 transport roots that way also. 



The above letter was pinned to the following note by Mr. Darwin. 



In answer to this show from similarity of American, 

 and European and Alpine-Arctic plants, that they have 

 travelled enormously without any change. 



As sub-arctic, temperate and tropical are all slowly march- 

 ing toward the equator, the tropical will be first checked 

 and distressed, similarly 1 the temperate will invade . . . ; 

 after the temperate can [not] advance or do not wish to 

 advance further the arctics will be checked and will invade. 

 The temperates will have been far longer in Tropics than 

 sub-arctics. The sub-arctics will first have to cross temperate 

 [zone] and then Tropics. They would penetrate among 

 strangers, just like the many naturalised plants brought by 

 man, from some unknown advantage. But more, for nearly 

 all have chance of doing so. 



'& 



The point of view is more clearly given in the following letters. 



Letter 334 To J. D. Hooker. 



Down, Nov. 15th [1856J. 

 I shall not consider all your notes on my MS. for some 

 weeks, till I have done with crossing ; but I have not been 

 able to stop myself meditating on your powerful objection to 

 the mundane cold period, 2 viz. that Mti/ry-iold more of the 

 warm-temperate species ought to have crossed the Tropics 

 than of the sub-arctic forms. I really think that to those 

 who deny the modification of species this would absolutely 

 disprove my theory. But according to the notions which I 

 am testing — viz. that species do become changed, and that 

 time is a most important element (which I think I shall be 



1 Almost illegible. 

 s See Letter 49. 



