386 GROWTH OF THE 'ORIGIN.' [1844. 



which are, I fancy, rather more confined. Can St. Plelena be 

 classed, though remotely, either with Africa or S. America.'* 

 From some facts, which I have collected, I have been led to 

 conclude that the fauna of mountains are either remarkably 

 similar (sometimes in the presence of the same species and at 

 other times of same genera), or that they are remarkably dis- 

 similar ; and it has occurred to me that possibly part of this 

 peculiarity of the St. Helena and Galapagos floras may be 

 attributed to a great part of these two Floras being moun- 

 tain Floras. I fear my notes will hardly serve to distinguish 

 much of the habitats of the Galapagos plants, but they may 

 in some cases ; most, if not all, of the green, leafy plants 

 come from the summits of the islands, and the thin brown 

 leafless plants come from the lower arid parts : would you be 

 so kind as to bear this remark in mind, when examining my 

 collection. 



I will trouble you with only one other question. In dis- 

 cussion with Mr. Gould, I found that in most of the genera 

 of birds which range over the whole or greater part of the 

 world, the individual species have wider ranges, thus the Owl 

 is mundane, and many of the species have very wide ranges. 

 So I believe it is with land and fresh-water shells — and I 

 might adduce other cases. Is it not so with Cryptogamic 

 plants ; have not most of the species wide ranges, in those 

 genera which are mundane ? I do not suppose that the 

 converse holds, viz. — that when a species has a wide range, 

 its genus also ranges wide. Will you so far oblige me by 

 occasionally thinking over this ? It would cost me vast 

 trouble to get a list of mundane phanerogamic genera and 

 then search how far the species of these genera are apt to 

 range wide in their several countries ; but you might occa- 

 sionally, in the course of your pursuits, just bear this in mind, 

 though perhaps the point may long since have occurred to 

 you or other Botanists. Geology is bringing to light interest- 

 ing facts, concerning the ranges of shells; I think it is pretty 

 well established, that according as the geographical range of 

 a species is wide, so is its persistence and duration in time. I 



