More Letters of Charles Darwin, Vol. 2

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Author: Charles Darwin

Letter 661. To P.H. Gosse.

(661/1. The following was written in reply to Mr. Gosse’s letter of May 30th asking for a solution of his difficulties in fertilising Stanhopea. It is reprinted by the kind permission of Mr. Edmund Gosse from his delightful book, the "Life of Philip Henry Gosse," London, 1890, page 299.)

Down, June 2nd, 1863.

It would give me real pleasure to resolve your doubts, but I cannot. I can give only suspicions and my grounds for them. I should think the nonviscidity of the stigmatic hollow was due to the plant not living under its natural conditions. Please see what I have said on Acropera. An excellent observer, Mr. J. Scott, of the Botanical Gardens, Edinburgh, finds all that I say accurate, but, nothing daunted, he with the knife enlarged the orifice and forced in pollen-masses; or he simply stuck them into the contracted orifice without coming into contact with the stigmatic surface, which is hardly at all viscid, when, lo and behold, pollen-tubes were emitted and fine seed capsules obtained. This was effected with Acropera Loddigesii; but I have no doubt that I have blundered badly about A. luteola. I mention all this because, as Mr. Scott remarks, as the plant is in our hot-houses, it is quite incredible it ever could be fertilised in its native land. The whole case is an utter enigma to me. Probably you are aware that there are cases (and it is one of the oddest facts in Physiology) of plants which, under culture, have their sexual functions in so strange a condition, that though their pollen and ovules are in a sound state and can fertilise and be fertilised by distinct but allied species, they cannot fertilise themselves. Now, Mr. Scott has found this the case with certain orchids, which again shows sexual disturbance. He had read a paper at the Botanical Society of Edinburgh, and I daresay an abstract which I have seen will appear in the "Gardeners’ Chronicle"; but blunders have crept in in copying, and parts are barely intelligible. How insects act with your Stanhopea I will not pretend to conjecture. In many cases I believe the acutest man could not conjecture without seeing the insect at work. I could name common English plants in this predicament. But the musk-orchis [Herminium monorchis] is a case in point. Since publishing, my son and myself have watched the plant and seen the pollinia removed, and where do you think they invariably adhere in dozens of specimens?—always to the joint of the femur with the trochanter of the first pair of legs, and nowhere else. When one sees such adaptation as this, it would be hopeless to conjecture on the Stanhopea till we know what insect visits it. I have fully proved that my strong suspicion was correct that with many of our English orchids no nectar is excreted, but that insects penetrate the tissues for it. So I expect it must be with many foreign species. I forgot to say that if you find that you cannot fertilise any of your exotics, take pollen from some allied form, and it is quite probable that will succeed. Will you have the kindness to look occasionally at your bee- Ophrys near Torquay, and see whether pollinia are ever removed? It is my greatest puzzle. Please read what I have said on it, and on O. arachnites.
I have since proved that the account of the latter is correct. I wish I could have given you better information.

P.S.—If the Flowers of the Stanhopea are not too old, remove pollen-masses from their pedicels, and stick them with a little liquid pure gum to the stigmatic cavity. After the case of the Acropera, no one can dare positively say that they would not act.

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Chicago: Charles Darwin, "Letter 661. To P.H. Gosse.," More Letters of Charles Darwin, Vol. 2, ed. Darwin, Francis, Sir, 1848-1925 and Seward, A. C. (Albert Charles), 1863-1941 and trans. Babington, B. G. (Benjamin Guy), 1794-1866 in More Letters of Charles Darwin Original Sources, accessed April 21, 2018, http://www.originalsources.com/Document.aspx?DocID=CK5VIMPFP6QCD4T.

MLA: Darwin, Charles. "Letter 661. To P.H. Gosse." More Letters of Charles Darwin, Vol. 2, edited by Darwin, Francis, Sir, 1848-1925 and Seward, A. C. (Albert Charles), 1863-1941, and translated by Babington, B. G. (Benjamin Guy), 1794-1866, in More Letters of Charles Darwin, Vol. 2, Original Sources. 21 Apr. 2018. www.originalsources.com/Document.aspx?DocID=CK5VIMPFP6QCD4T.

Harvard: Darwin, C, 'Letter 661. To P.H. Gosse.' in More Letters of Charles Darwin, Vol. 2, ed. and trans. . cited in , More Letters of Charles Darwin. Original Sources, retrieved 21 April 2018, from http://www.originalsources.com/Document.aspx?DocID=CK5VIMPFP6QCD4T.