To Asa Gray 18 June 1
Down Bromley Kent
My dear Dr. Gray
I must thank you for your two very valuable letters.2 It is extremely kind of you to say that my letters have not bored you very much, & it is almost incredible to me, for I am quite conscious that my speculations run quite beyond the bounds of true science. One chief object of this note is to say that I have not received the last part of your Silliman Papers:3 Hooker has, & he says he will lend it me, if, as is very likely, you have not another copy. But it may come with the Watson correspondence.—4 Your remarks on that head will be of real use to me, when I return to the subject, for a man must be blind not to see how cautious a reasoner you are.
Thank you much for your remarks on disjoined species:5 I daresay I may be quite in error: I saw so much difficulty even theoretically & so much impossibility practically from my ignorance, that I had given up notion till I read your note to your Article. I had only just copied out a few striking cases out of Hooker’s Him: Journal6 & turned to Steudel7 to see what the genera were. The notion was grounded on the belief that disjoined species had suffered much local extinction & therefore (conversely with the case of genera with many species having species with wide ranges.) I inferred that genera & Families with very few species (ie from Extinction) would be apt (not necessarily always) to have narrow ranges & disjoined ranges. You will not perceive, perhaps, what I am driving at & it is not worth enlarging on,—but I look at Extinction as common cause of small genera & disjoined ranges & therefore they ought, if they behaved properly & as nature does not lie to go together!—8
I have not the least doubt that the proportions of British naturalised plants were due to simple chance; but I thought it was just worth mentioning to you: I had from your former Edition of Manual quite given up idea.—
It has been extremely kind of you telling me about the trees: now with your facts, & those from Britain, N. Zealand, & Tasmania, I shall have fair materials for judging:9 I am writing this away from home,10 but I think your fraction of 95132 is as large as in other cases, & 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, & then I wished to make out how far in animals & vegetables this was possible.— Papilionaceous flowers are almost dead floorers to me, & I cannot experimentise as castration alone often produces sterility. I am surprised at what you say about Compositæ & Gramineæ. From what I have seen of latter they seemed to me (& I have watched Wheat owing to what L. Deslongchamps has said on their fertilisation in bud)11 favourable for crossing; & from Cassini’s observations12 & Kölreuters13 on the adhesive pollen & C. C. Sprengels’,14 I had concluded that the Compositæ were eminently likely (I am aware of the pistil brushing out pollen.) to be crossed. 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 shd be very glad to hear, as it wd. save me from great blunder. In several published remarks on this subject in various genera it has seemed to me that the early fertilisation has been inferred from the early shedding of the pollen, which I think is clearly false inference. Another cause, I shd. think, of the belief of fertilisation in the bud, is the not-rare abnormal early maturity of the pistil, as described by Gærtner.—15 I have hitherto failed in meeting with detailed account of regular & normal impregnation in the bud.— Podostemon & Subularia under water (& Leguminosæ) seem & are strongest cases against me, as far as I as yet know.
I am so sorry that you are so overwhelmed with work; it makes your very great kindness to me the more striking. Believe me, Your’s gratefully | C. Darwin
It is really pretty to see how effectual insects are: a short time ago I found a female Holly 60 measured yards from any other Holly & I cut off some twigs & took by chance 20 stigmas, cut off their tops & put them under microscope: there was pollen on every one & in profusion on most! Weather cloudy & stormy & unfavourable, wind in wrong direction to have brought any.16
Thanks for AG’s remarks on disjoined species. CD’s notions are based on belief that disjoined species have suffered much extinction, which is the common cause of small genera and disjoined ranges.
Discusses out-crossing in plants.
Has failed to meet with a detailed account of regular and normal impregnation in the bud. Podostemon, Subularia, and underwater Leguminosae are the strongest cases against him.