1843—1882] CLOSE SPECIES 421 



Asa Gray to C. Darwin. 1 Letter 324 



Harvard University, Cambridge, U.S., June 30th, 1855. 



Your long letter of the 8th inst. is full of interest to me, 

 and I shall follow out your hints as far as I can. I rejoice 

 in furnishing facts to others to work up in their bearing on 

 general questions, and feel it the more my duty to do so 

 inasmuch as from preoccupation of mind and time and want 

 of experience I am unable to contribute direct original in- 

 vestigations of the sort to the advancement of science. 



Your request at the close of your letter, which you have 

 such needless hesitation in making, is just the sort of one 

 which it is easy for me to reply to, as it lies directly in my 

 way. It would probably pass out of my mind, however, at 

 the time you propose, so I will attend to it at once, to fill up 

 the intervals of time left me while attending to one or two 

 pupils. So I take some unbound sheets of a copy of the 

 Manual, and mark off the " close species " by connecting 

 them with a bracket. 



Those thus connected, some of them, I should in revision 

 unite under one, many more Dr. Hooker would unite, and 

 for the rest it would not be extraordinary if, in any case, the 

 discovery of intermediate forms compelled their union. 



As I have noted on the blank page of the sheets I send 

 you (through Sir William Hooker), I suppose that if we 

 extended the area, say to that of our flora of North America, 

 we should find that the proportion of " close species " to the 

 whole flora increased considerably. But here I speak at a 

 venture. Some day I will test it for a few families. 



If you take for comparison with what I send you, the 

 British Flora, or Koch's Flora Germanica, or Godron's Flora 

 of France, and mark the " close species " on the same principle, 

 you will doubtless find a much greater number. Of course 

 you will not infer from this that the two floras differ in this 

 respect ; since the difference is probably owing to the facts 

 that (1) there have not been so many observers here bent upon 

 detecting differences ; and (2) our species, thanks mostly to 

 Dr. Torrey and myself, have been more thoroughly castigated. 

 What stands for one species in the Manual would figure in 



1 In reply to Darwin's letter, June 8th, 1S55, given in Life and I ettcrs, 

 II., p. 61. 



