434 GEOGRAPHICAL DISTRIBUTION [CHAP. VI 



Letter 331 and I know of only one essay (viz. Hooker's " New Zealand ") 

 that makes any approach to the clearness with which your 

 paper makes a non-botanist appreciate the character of the 

 flora of a country. It is wonderfully condensed (what labour 

 it must have required !). You ask whether such details are 

 worth giving : in my opinion, there is literally not one word 

 too much. 



I thank you sincerely for the information about " social ' 

 and " varying plants," and likewise for giving me some idea 

 about the proportion (i.e. Jth) of European plants which you 

 think do not range to the extreme North. This proportion 

 is very much greater than I had anticipated, from what I 

 picked up in conversation, etc. 



To return to your " Statistics." I dare say you will give 

 how many genera (and orders) your 260 introduced plants 

 belong to. I see they include 113 genera non-indigenous. 

 As you have probably a list of the introduced plants, would 

 it be asking too great a favour to send me, per Hooker or 

 otherwise, just the total number of genera and orders to 

 which the introduced plants belong. I am much interested 

 in this, and have found De Candolle's remarks on this subject 

 very instructive. 



Nothing has surprised me more than the greater generic 

 and specific affinity with East Asia than with West America. 

 Can you tell me (and I will promise to inflict no other 

 question) whether climate explains this greater affinity? or 

 is it one of the many utterly inexplicable problems in 

 botanical geography? Is East Asia nearly as well known 

 as West America? so that does the state of knowledge 

 allow a pretty fair comparison ? I presume it would be 

 impossible, but I think it would make in one point your 

 tables of generic ranges more clear (admirably clear as they 

 seem to me) if you could show, even roughly, what pro- 

 portion of the genera in common to Europe (i.e. nearly half) 

 are very general or mundane rangers. As your results now 

 stand, at the first glance the affinity seems so very strong to 

 Europe, owing, as I presume, to nearly half of the genera 

 including very many genera common to the world or 

 large portions of it. Europe is thus unfairly exalted. Is 

 this not so? If we had the number of genera strictly, or 

 nearly strictly European, one could compare better with 



