To Fritz Müller [late December 1866 and] 1 January 18671
Down. | Bromley. | Kent. S.E.
My dear Sir
Your letter of Nov 2. contains an extraordinary amount of interesting matter.2 What a number of dimorphic plants S. Brazil produces; you observed in one day as many or more dimorphic genera than all the botanists in Europe have ever observed.3 When my present book is finished I shall write a final paper upon these plants, so that I am extremely glad to hear of your observations & to see the dried flowers; nevertheless I shd regretrvations & to see the dried flowers; nevertheless I shd regret much if I prevented you from publishing on the subject. Plumbago is quite new to me, though I had suspected it.4
It is curious how dimorphism prevails by groups throughout the world, shewing as I suppose that it is an ancient character: thus Hedyotis is dimorphic in India: the two other genera in the same sub-family with Villarsia are dimorphic in Europe & Ceylon: a sub-genus of Erythroxylum is dimorphic in Ceylon ?& Oxalis with you & at the C. of Good Hope5 If you can find a dimorphic Oxalis it will be a new point, for all known species are trimorphic or monomorphic.6 The case of Convolvulus will be new if proved.7 I am doubtful about Gesneria & have been often myself deceived by varying length of pistil.8 A difference in the size of the pollen-grains wd be conclusive evidence; but in some cases experiments by fertilization can alone decide the point. As yet I know of no case of dimorphism in flowers which are very irregular; such flowers being apparently always sufficiently visited & crossed by insects. Your case of the Eschholtzia is extremely curious.9 With Orchids I know of many facts like that which you give about Oncidium.10
Will you be so kind as to remember to tell me, when you next write, whether the Oncidium is an endemic species.
I do not know what to think about yr curious speculation on the retarded fertilization of certain Orchids: I believe the pollen-tubes do not reach the ovule in some coniferous trees until many months have elapsed.11 The little bulbs of the semi-sterile Oxalis have begun to grow & I hope will flower;12 I shd suspect that their sterility was nearly of the same nature with that of many cultivated plants.
I have sent off Bentham’s & Hooker’s Genera by post to you.13 With respect to the scarlet seeds sent in a former letter I gave 2 to a fowl but they were ground up by its gizzard & disappeared. The remainder I sent to Dr Hooker; he knows the seeds well, & says they belong to an Indian plant the Adenanthera pavonina.14 Is it a garden-plant with you? The dissemination of its seeds is a puzzling problem.
With cordial thanks for all yr great kindness believe me yours very sincerely | Charles Darwin
P.S. Jan 1 1867
By some unaccountable delay I have only this moment received copies of your paper. I will send off 3 copies as before stated;15 I transmit to you by this post 11 copies; I retain 10 copies any or all of which I will send as you may direct.
Thanks for observations on dimorphic plants. Dimorphism prevalent in certain groups throughout the world.
Retarded fertilisation in certain orchids.
Please cite as
Darwin Correspondence Project, “Letter no. 5331,” accessed on 27 October 2016, http://www.darwinproject.ac.uk/DCP-LETT-5331