252 BOTANY [CHAP. X 



Letter 585 To Asa Gray. 



Down [1857]. 



I am very glad to hear that you think of discussing the 

 relative ranges of the identical and allied U. States and Euro- 

 pean species, when you have time. Now this leads me to 

 make a very audacious remark in opposition to what I imagine 

 Hooker has been writing, 1 and to your own scientific conscience. 

 I presume he has been urging you to finish your great Flora 

 before you do anything else. Now I would say it is your 

 duty to generalise as far as you safely can from your as 

 yet completed work. Undoubtedly careful discrimination of 

 species is the foundation of all good work ; but I must look 

 at such papers as yours in Silliman as the fruit. As careful 

 observation is far harder work than generalisation, and still 

 harder than speculation, do you not think it very possible 

 that it may be overvalued ? It ought never to be forgotten 

 that the observer can generalise his own observations incom- 

 parably better than any one else. How many astronomers 

 have laboured their whole lives on observations, and have not 

 drawn a single conclusion ; I think it is Herschel who has 

 remarked how much better it would be if they had paused 

 in their devoted work and seen what they could have deduced 

 from their work. So do pray look at this side of the ques- 

 tion, and let us have another paper or two like the last 

 admirable ones. There, am I not an audacious dog ! 



You ask about my doctrine which led me to expect that 

 trees would tend to have separate sexes. I am inclined to 

 believe that no organic being exists which perpetually self- 

 fertilises itself. This will appear very wild, but I can venture 

 to say that if you were to read my observations on this sub- 

 ject you would agree it is not so wild as it will at first appear 

 to you, from flowers said to be always fertilised in bud, etc. 

 It is a long subject, which I have attended to for eighteen 

 years. Now, it occurred to me that in a large tree with 

 hermaphrodite flowers, we will say it would be ten to one that 

 it would be fertilised by the pollen of its own flower, and 

 a thousand or ten thousand to one that if crossed it would 

 be crossed only with pollen from another flower of same tree, 

 which would be opposed to my doctrine. Therefore, on the 



1 See Letter 338, Vol. I., p. 443- 



