To Asa Gray 14 July 1
Down Bromley Kent
My dear Gray
I shd. have returned the enclosed sooner;2 but we have had had a miserable ten days. Our Boy (the Postage Stamp collector) has had a return of Scarlet fever, with all sorts of mischief, kidneys, glands of neck &c & still has much fever.3 But he is now made up for night & I will try & forget the misery of this weary world, & write a bit about science.—
With respect to Pogonia, it would be a very great anomaly, if insects open the anther for nectar: you say nothing about the rostellum;4 from Vanilla I shd. expect that viscid matter would be forced under lip of anther. Insects ought to be watched at work. In Australia Bees open the indusium of Goodeniaceæ for pollen.—5 Platanthera fimbriata is a pretty case.6 There is no end to the adaptations. Ought not these cases to make one very cautious when one doubts about the use of all parts?— I fully believe that the structure of all irregular flowers is governed in relation to insects. Insects are the Lords of the floral (to quote the witty Athenæum) world.—7 How well you have worked the N. American Orchids! I am heartily glad by this time that your harassing Lectures are over.8
Hooker is very anxious about Mrs Hooker & has started on health-tour to Switzerland.9 Today I heard of the sudden death of poor old Prof. Bronn, just as he finished translating my orchid-book.10 There is misery & anxiety everywhere.— Poor dear Hooker seemed very anxious.—
A few days ago I made an observation which has surprised me more that it ought to do— it will have to be repeated several times, but I have scarcely a doubt of its accuracy.— I stated in my Primula paper that the long-styled form of Linum grandiflorum was utterly sterile with own pollen;11 & I have lately been putting the pollen of the two forms on the division of the stigma of the same flower; & it strikes me as truly wonderful, that the stigma distinguishes the pollen; & is penetrated by the tubes of the one & not by those of the other; nor are the tubes exserted. Or, (which is the same thing) the stigma of the one form acts on & is acted by (for the papillæ become colourless) pollen, which produces not the least effect on the stigma of the other form. Taking sexual power as the criterion of difference the two forms of this one species may be said to be generically distinct.—12
Farewell my dear friend | C. Darwin
Adaptations of orchid flowers. Believes the structure of all irregular flowers is adaptation to insect fertilisation.
Linum grandiflorum distinguishes its own pollen so that when placed on stigma of same flower the pollen-tube is not even exserted.
Please cite as
Darwin Correspondence Project, “Letter no. 3656,” accessed on 23 March 2017, http://www.darwinproject.ac.uk/DCP-LETT-3656