From Friedrich Hildebrand 23 October 1866
Oct 23d | 1866.
Dear and honoured Sir
I received your kind letter this morning, but I am very sorry that I cannot satisfy your wishes about the seeds of Oxalis rosea, I spent all of them this spring to see what forms I might get from the seeds produced by the three different manners of fertilisation—all of them were long-styled like the mother-plants.1 I have not made any other experiments about this matter and I am really sorry that I cannot send you the wanted seeds.— Perhaps it will interest you that I have experimentized last summer, besides other plants, with the flowers of Aristolochia Clematitis.2 Sprengel has made a mistake when thinking that each flower of this species is fertilised by insects agency with its own pollen.3 My observation have shown to me quite the contrary, for we have here a very interesting and curious case of “weiblich-männlich Dichogamia.4 When the flower openes only the stigma is ripe, the anthers are not opened as yet and besides secured by the form of the kettle from the insect’s touch. Some time after this first state of the flower the stigmatic surface besides withering is turned upwards and rolled up in a way that it cannot be touched any more, now the anthers open and can be touched by the insect because the under part of the kettle has become larger and is moved away from them. Now the hairs in the corollas mouth wither and the little flies get out, covered with pollen, to bring it now to the open stigma of a younger flower; the fertilisation with the flowers own pollen is quite impossible.
This case of dichogamie is quite different from the others known as yet, because the insect must wait in the flower the stigma of which it has fertilised, till the anthers of this same flower are opened— I hope that I shall be able to publish some thing about this matter, where the figures will make clearer this curious construction—but I fear it shall last again some time before I can sent you something about it;5 you have seen how long the publication of my paper on Oxalis has been delayed, that was written on the end of the last year.6
I was very glad to see by the letter written with your own hand that you are recovered now, sending you my best wishes for your further health7
I remain | dear Sir | yours | truly | F Hildebrand
Explains dichogamy in Aristolochia. C. K. Sprengel was wrong.
Please cite as
Darwin Correspondence Project, “Letter no. 5254,” accessed on 1 May 2016, http://www.darwinproject.ac.uk/DCP-LETT-5254