254 BOTANY [CHAP. X 



Letter 585 Australian gardener : viz., how odd it was that his Erythrinas 

 in N. S. Wales would not set a seed, without he imitated the 

 movements of the petals which bees cause. Well, as long as 

 you live, you will never, after this fearfully long note, ask me 

 why I believe this or that. 



Letter 586 To Asa Gray. 



June i8th [1857]. 



It has been extremely kind of you telling me about the 

 trees : now with your facts, and those from Britain, N. Zealand, 

 and Tasmania I shall have fair materials for judging. I am 

 writing this away from home, but I think your fraction of 

 T 9 /^ is as large as in other cases, and is at least a striking 

 coincidence. 



I thank you much for your remarks about my crossing 

 notions, to which, I may add, I was led by exactly the same 

 idea as yours, viz., that crossing must be one means of 

 eliminating variation, and then I wished to make out how far 

 in animals and vegetables this was possible. Papilionaceous 

 flowers are almost dead floorers to me, and I cannot experi- 

 mentise, as castration alone often produces sterility. I am 

 surprised at what you say about Compositae and Gramineae. 

 From what I have seen of latter they seemed to me (and 

 I have watched wheat, owing to what L. de Longchamps has 

 said on their fertilisation in bud) favourable for crossing ; and 

 from Cassini's observations and Kolreuter's on the adhesive 

 pollen, and C. C. Sprengel's, I had concluded that the 

 Compositae were eminently likely (I am aware of the pistil 

 brushing out pollen) to be crossed. 1 If in some months' time 

 you can find time to tell me whether you have made any 

 observations on the early fertilisation of plants in these two 

 orders, I should be very glad to hear, as it would save me from 

 great blunder. In several published remarks on this subject 

 in various genera it has seemed to me that the early fertilisa- 

 tion has been inferred from the early shedding of the pollen, 

 which I think is clearly a false inference. Another cause, 

 I should think, of the belief of fertilisation in the bud, is the 



1 This is an instance of the curious ignorance of the essential principles 

 of floral mechanism which was to be found even among learned and 

 accomplished botanists such as Gray, before the publication of the 

 Fertilisation of Orchids. Even in 1863 we find Darwin explaining the 

 meaning of dichogamy in a letter to Gray. 



