gS THE UNFINISHED BOOK. [1857U 



able. Will you turn this in your mind ? it is an important 

 apparent law (!) for me. 



Ever yours, 



C. Darwin. 



P.S. I do not know how far you will care to hear, but 

 I find Moquin-Tandon treats in his ' Teratologic ' on villosity 

 of plants, and seems to attribute more to dryness than 

 altitude ; but seems to think that it must be admitted that 

 mountain plants are villose, and that this villosity is only 

 in part explained by De Candolle's remark that the dwarfed 

 condition of mountain plants would condense the hairs, and 

 so give them the appearci7ice of being more hairy. He quotes 

 Senebier, ' Physiologie Vegetale,' as authority I suppose 

 the first authority, for mountain plants being hairy. 



If I could show positively that the endemic species were 

 more hairy in dry districts, then the case of the varieties 

 becoming more hairy in dry ground would be a fact for me. 



C. Darwin to J. D. Hooker. 



Down, June 3rd [185 7 J. 

 My DEAR HOOKER, I am going to enjoy myself by 

 having a prose on my own subjects to you, and this is a 

 greater enjoyment to me than you will readily understand, as 

 I for months together do not open my mouth on Natural 

 History. Your letter is of great value to me, and staggers me 

 in regard to my proposition. I dare say the absence of 

 botanical facts may in part be accounted for by the difficulty 

 of measuring slight variations. Indeed, after writing, this 

 occurred to me ; for I have Crucianella stylosa coming into 

 flower, and the pistil ought to be very variable in length, and 

 thinking of this I at once felt how could one judge whether it 

 was variable in any high degree. How different, for instance, 

 from the beak of a bird ! But I am not satisfied with this ex- 

 planation, and am staggered. Yet I think there is something 



