To P. H. Gosse 2 June 1
Down. | Bromley. | Kent. S.E.
My dear Sir
It would give me real pleasure to resolve your doubts, but I cannot. I can give only suspicions & my grounds for them. I should think the non-viscidity of the stigmatic hollow was due to the plant not living under its natural conditions.2 Please see what I have said on Acropera;3 an excellent observer Mr. J. Scott of Bot. Garden Edinburgh finds all that I say accurate, but nothing daunted he with the knife enlarged orifice & 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 & behold pollen-tubes were emitted & fine seed capsules obtained.4 This was effected with Acropera Loddigesii; but I have no doubt that I have blundered badly about A. luteola.5 I mention all this because as Mr Scott remarks, as the plant is in our Hot-House it is quite incredible it ever could be fertilised in its native land.6 The whole case is an utter enigma to me.—7
Probably you are aware that there are cases (& 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 & ovules are in sound state & can fertilise & be fertilised by distinct but allied species; they cannot fertilise themselves.8 Now Mr Scott has found this the case with certain Orchids, which again shows sexual disturbance. He has read paper at Bot. Soc. of Edinburgh & I daresay an abstract which I have seen will appear in Gard. Chron; but blunders have crept in in copying & parts are barely intelligible.9 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 is case in point. Since publishing my son & self have watched the plant & seen the pollinia removed & where do you think they invariably adhere in dozens of specimens; always to the joint of femur with the trochanter of 1st. pair of legs & no where else.10 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.11 So I suspect it must be with many foreign species.
I forgot to say, that if you find you cannot fertilise any of your exotics take pollen from some allied form & it is quite probable that will succeed.—
Will you have the kindness to look occasionally at your Bee Ophrys near Torquay & see whether pollinia are ever removed. It is my greatest puzzle.12 Please read what I have said on it & on O. arachnites;13 I have since proved account of latter is correct.14 I wish I could have given you better information.
My dear Sir | Yours sincerely | Ch. Darwin
P.S. | If the flowers of the Stanhopea are not too old—remove pollen-masses from their pedicels & stick them with a little liquid pure gum to stigmatic cavity. After the case of the Acropera, no one can dare positively say that they would not act.—
Can only conjecture that the problem occurs because the plant is not living in its natural conditions. Refers to what he said on Acropera [in Orchids]. Many plants under culture have sexual functions altered.
Asks PHG to look at bee Ophrys at Torquay to see if pollinia are ever removed. "It is my greatest puzzle."
- Letter no.
- Darwin, C. R.
- Gosse, P. H.
- Sent from
- Source of text
- The Brotherton Collection, Leeds University Library
- Physical description
Please cite as
Darwin Correspondence Project, “Letter no. 4200,” accessed on 24 September 2016, http://www.darwinproject.ac.uk/DCP-LETT-4200