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Darwin Correspondence Project

To Fritz Müller   26 May [1867]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


The year is established by the relationship between this letter and the letter from Fritz Müller, 1 April 1867.
In ‘Fertilization of orchids’, p. 154 (Collected papers 2: 150), CD referred to Müller’s work on the structure and manner of cross-fertilisation of orchids in Brazil but stated that he had not had ‘space or time to give an abstract of his many discoveries’. CD cited Müller frequently in the second edition of Orchids for information that Müller had sent him.
See letter from Fritz Müller, 1 April 1867. Müller had discovered that when he tried to self-pollinate self-sterile species, the pollen placed on the stigma became discoloured and decayed, whereas when a cross was attempted between distinct plants of the same species or of different species, the pollen stayed fresh (see also Variation 2: 134–5).
CD discussed Müller’s findings in Variation 2: 134–5.
CD refers to Hildebrand 1866a. For Müller’s suggestion that Corydalis might be dimorphic, see the letter from Fritz Müller, 1 April 1867.
Müller had sent CD seeds of Plumbago (letter to J. D. Hooker, 24 [March 1867]), possibly with his letter of 2 February 1867; he sent seed of Gesneria with his letter of 1 January 1867.
Max Kuhn made this announcement in his article ‘Einige Bemerkungen über Vandellia und den Blüthenpolymorphismus’ (Botanische Zeitung, 1 March 1867, p. 67). There is an annotated copy of this issue in the Darwin Pamphlet Collection–CUL.
CD probably refers to John Dominy, a gardener for James Veitch & Son, who produced the first known artificial orchid hybrid, between Calanthe furcata and C. masuca, in 1856. Orchid hybrids were produced only at Veitch & Son’s nursery for fifteen years. See Shephard 2003, pp. 127–9; see also Correspondence vol. 10, letter from J. D. Hooker, [23–5 March 1862] and n. 3.
Müller had estimated that a seed capsule of Maxillaria contained well over one and a half million seeds (see Correspondence vol. 14, letter from Fritz Müller, 1 and 3 October 1866; see also ‘Fertilization of orchids’, p. 158 (Collected papers 2: 155), and Orchids 2d ed., p. 278).
CD was working on the page-proofs of Variation.


Collected papers: The collected papers of Charles Darwin. Edited by Paul H. Barrett. 2 vols. Chicago and London: University of Chicago Press. 1977.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

‘Fertilization of orchids’: Notes on the fertilization of orchids. By Charles Darwin. Annals and Magazine of Natural History 4th ser. 4 (1869): 141–59. [Collected papers 2: 138–56.]

Orchids 2d ed.: The various contrivances by which orchids are fertilised by insects. By Charles Darwin. 2d edition, revised. London: John Murray. 1877.

Orchids: On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing. By Charles Darwin. London: John Murray. 1862.

Shephard, Sue. 2003. Seeds of fortune: a gardening dynasty. London: Bloomsbury.

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.


Thanks for information on sexual differences.

Orchids; self-sterility and difficulty of getting seeds to germinate.


Letter details

Letter no.
Charles Robert Darwin
Johann Friedrich Theodor (Fritz) Müller
Sent from
Source of text
The British Library (Loan MS 10 no 16)
Physical description
LS 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 5551,” accessed on 26 September 2022,

Also published in The Correspondence of Charles Darwin, vol. 15