To Fritz Müller 26 May 1
Down. | Bromley. | Kent. S.E. May 26 My dear Sir
I thank you much for your information on sexual differences with the pretty little sketch of the male crab, & for the great trouble which you have taken in copying the long extract from Claus,2 All such facts interest me much. I shall also be very glad for answers to any of my questions on the expression of negros.3 Your additions about the self-sterile orchids are particularly valuable, & I shall give an abstract of all the information which you have so kindly given me.4 The comparison of the pollen with that when species are crossed makes the facts much more curious.5 The analogous cases which have been observed in Europe I have always attributed to the unnatural condition under which the orchids were grown; but it now appears that this is an error; I fear however that I shall not be able to alter the place in my book where I give these facts.6 As Dr Hildebrand in experimenting on Corydalis used the pollen from several individuals & always with the same result I do not think the species can be dimorphic.7
Only 3 plants of your Plumbago are alive, but they are doing well. Hundreds of yr Gesnera have germinated.8 Kuhn announces in the Bot. Zeitung that he is going to publish a work on dimorphic plants of all kinds, but as far as I can judge, he does not experiment, & therefore will not interfere with me.9
I dare say your observations in crossing orchids will be very interesting; they already illustrate most of the leading laws; but I fear their interest will be greatly lessened by the crossed seeds not germinating. One single man in Europe has found out how to make these seeds germinate, & he keeps it a secret in his trade of nurseryman.10 He also has made some strange crosses between distinct genera, & these hybrids have flowered.
Dr Hooker tells me that they have in vain tried at Calcutta to make the seeds of hybrids germinate;11 yet American orchids growing in the Bot. Garden there have spontaneously sown themselves and grown on adjoining trees.
I presume this strange difficulty in making the seeds germinate explains their astonishing number, which you and others have shewn.12 I am not able to do much this summer in experimenting as all my time is taken up in getting my book thro’ the press;13 it progresses very slowly & is I fear hardly worth the great labour it costs me.
With cordial thanks for your never failing kindness I remain my dear Sir | yours very sincerely | Ch. Darwin
Thanks for information on sexual differences.
Orchids; self-sterility and difficulty of getting seeds to germinate.
Please cite as
Darwin Correspondence Project, “Letter no. 5551,” accessed on 5 December 2016, http://www.darwinproject.ac.uk/DCP-LETT-5551