To Fritz Müller 25 September 1
Down Bromley Kent
Sep & 25th
My dear Sir
I have just recd your letter of Aug. 2nd & am as usual astonished at the number of interesting points which you observe. It is quite curious how by coincidence you have been observing the same subjects that have lately interested me.2
Your case of the Notylia is quite new to me; but it seems analogous with that of Acropera, about the sexes of which I blundered greatly in my book.3 I have got an Acropera now in flower & have no doubt that some insect with a tuft of hairs on its tail removes by the tuft the pollinia, & inserts the little viscid cap & the long pedicel into the narrow stigmatic cavity, & leaves it there with the pollen-masses in close contact with, but not inserted into, the stigmatic cavity. I find I can thus fertilize the flowers; & so I can with Stanhopea, & I suspect that this is the case with your Notylia.4 But I have lately had an orchid in flower, viz. Acineta, which I could not any how fertilize.5 Dr Hildebrand lately wrote a paper shewing that with some orchids the ovules are not mature & are not fertilized until months after the pollen-tubes have penetrated the column; & you have independently observed the same fact, which I never suspected in the case of Acropera.6 The column of such orchids must act almost like the Spermatheca of insects. Your Orchis with 2 leaf-like stigmas is new to me; but I feel guilty at your wasting your valuable time in making such beautiful drawings for my amusement.7
Your observations on those plants being sterile which grow separately or flower earlier than others are very interesting to me. They wd be worth experimenting on with other individuals: I shall give in my next book several cases of individual plants being sterile with their own pollen. I have actually got on my list Escholtzia for fertilizing with its own pollen, though I did not suspect it wd prove sterile, & I will try next summer.8 My object is to compare the rate of growth of plants raised from seed fertilized by pollen from the same flower & by pollen from a distinct plant & I think from what I have seen I shall arrive at interesting results.9 Dr Hildebrand has lately described a curious case of Corydalis cava, which is quite sterile with its own pollen, but fertile with pollen of any other individual plant of the species.10 What I meant in my paper on Linum about plants being dimorphic in function alone was that they shd be divided into two equal bodies functionally but not structurally different.11 I have been much interested by what you say on seeds which adhere to the valves being rendered conspicuous: you will see in the new Edit. of the origin why I have alluded to the beauty & bright colours of fruit;12 after writing this, it troubled me that I remembered to have seen brilliantly coloured seed, & your view occurred to me. There is a species of Peony in which the inside of the pod is crimson & the seeds dark purple. I had asked a friend to send me some of these seeds, to see if they were covered with any thing which cd prove attractive to birds.13 I recd some seeds the day after receiving your letter; & I must own that the fleshy covering is so thin that I can hardly believe it wd lead birds to devour them; & so it was in an analogous case with Passiflora gracilis.14 How is this in the cases mentioned by you? The whole case seems to me rather a striking one.
I wish I had heard of Mikania being a leaf-climber before your paper was printed; for we thus get a good gradation from M. scandens to Mutisia with its little modified leaf-like tendrils.15 I am glad to hear that you can confirm (but render still more wonderful) Haeckel’s most interesting case of Liriope: Huxley told me that he thought that the case wd somehow be explained away.16
As for Agassiz & his glaciers in the valley of the Amazons, it seems to me sheer madness, as it does likewise to Lyell; the evidence being wholly insufficient.17 Prof. Asa Gray tells me that A. started with the determination to prove that the whole world had been covered with ice in order to annihilate all Darwinian views.18
I hope I have not troubled you with this long letter & believe me yours very sincerely
Fertilisation in orchids: Friedrich Hildebrand’s paper.
Agassiz’s attempts to eliminate all Darwinian views.