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Darwin Correspondence Project

To Fritz Müller   [before 10 December 1866]1

Down Bromley Kent

My dear Sir

I have so much to thank you for that I hardly know how to begin. I have received the bulbillas of Oxalis & your most interesting letter of Oct 1st.2 I have planted half the bulbs & will plant the other half in the spring. The case seems to me very curious & until trying some experiments in crossing I can form no conjecture what the abortion of the stamens in so irregular a manner can signify.3 But I fear from what you say the plant will prove sterile like so many others which increase largely by buds of various kinds. Since I asked you about Oxalis Dr. Hildebrand has published a paper showing that a great number of species are trimorphic like Lythrum, but he has tried hardly any experiments.4

I am particularly obliged for the information & specimen of Cordia & shall be most grateful for seed: I have not heard of of any dimorphic species in this Family.5 Hardly anything in your letter interested me so much as your account & drawing of the valves of the pod of one of the Mimoseæ with the really beautiful seeds.— I will send some of these seeds to Kew to be planted.6 But these seeds seem to me to offer a very great difficulty. They do not seem hard enough to resist the triturating power of the gizard of a gallinaceous bird, though they might resist that of some other birds, for the skin is as hard as ivory. I presume that these seeds cannot be covered with any attractive pulp. I soaked one of the seeds for 10 hours, in warm water which became only very slig⁠⟨⁠htly⁠⟩⁠ mucilaginous. I think I will try whether they will pass through a fowl uninjured.7 I hope you will observe whether any bird devours them, & could you get any young man to shoot some & observe whether the seeds are found low down in the intestines. It would be well worth while to plant such seeds with undigested seeds for comparison. An opponent of ours might make a capital case against us by saying that here beautiful pods & seeds have been formed not for the good of the plant but for the good of birds alone. These seeds would make a beautiful bracelet for one of my daughters if I had enough. I may just mention that ⁠⟨⁠E⁠⟩⁠uonymus Europæus is a case in point; the seeds are coated by a thin orange layer which I find is sufficient to cause them to be devoured by birds.8 I have received your paper on Martha; it is as wonderful as the most wonderful orchis:9 Ernst Haeckel brought me the paper & stayed a day with me. I have seldom seen a more pleasant, cordial & frank man. He is now in Madeira where he is going to work chiefly on the Medusæ10   His great work is now published & I have a copy, but the german is so difficult I can make out but little of it, & I fear it is too large a work to be translated.11

Your fact about the number of seeds in the capsule of the Maxillaria came just at the right time as I wished to give one or two such facts.12 Does this orchid produce many capsules? I can not answer your question about the aerial roots of Catasetum.13 I hope you have received the new Edition of the “Origin”—14 Your paper on climbing plants is printed & I expect in a day or two to receive the spare copies, & I will send off three copies as before stated, & will retain some in case you should wish me to send them to anyone in Europe, & will transmit the remainder to yourself15

With cordial thanks for all your great kindness, believe me, | My dear Sir, | Yours sincerely | Ch. Darwin


The date is established by the relationship between this letter and the letter to J. D. Hooker, 10 December [1866] (see nn. 6 and 7, below).
See letter from Fritz Müller, 1 and 3 October 1866. ‘Bulbillas’: i.e. bulbils.
Müller had found that 99 per cent of the plants he had observed of one form of a species of Brazilian Oxalis had sterile anthers. The specimens with fertile anthers ranged from those with good pollen to those with aborted pollen-grains and ultimately to those with no pollen (see letter from Fritz Müller, 1 and 3 October 1866 and nn. 2 and 6).
CD refers to Hildebrand 1866c. See letter from Friedrich Hildebrand, 23 October 1866 and n. 1.
Cordia belongs to the family Boraginaceae. In Forms of flowers, pp. 117–18, CD described the specimens sent by Müller with his letter of 1 and 3 October 1866, concluding that they were probably heterostyled.
See letter from Fritz Müller, 1 and 3 October 1866. Müller had sent these seeds and seeds of a twining leguminous plant (see letter to J. D. Hooker, 5 December [1866]). CD enclosed some of the seeds (later identified by Joseph Dalton Hooker as Adenanthera pavonina) with his letter to J. D. Hooker, 10 December [1866].
CD recorded the trial feeding of these seeds to a fowl in his Experimental notebook (DAR 157a: 80) and reported the outcome of the experiment in his letter to J. D. Hooker, 10 December [1866].
CD had referred to spindle-wood (Euonymus europaeus), in arguing that beauty or bright colour in fruits and seeds had developed as a means of attracting birds and other animals who would eat and disseminate the seeds, in Origin 4th ed., p. 240.
The reference is to F. Müller 1866a, where Müller described the mechanism by which Martha fragrans prevented self-pollination. CD discussed the process in Cross and self fertilisation, p. 5; he referred to the plant as Posoqueria fragrans. Martha fragrans and Posoqueria fragrans are synonyms of Posoqueria latifolia subsp. latifolia.
Haeckel visited CD on 21 October 1866 (Emma Darwin’s diary (DAR 242)). For more on Haeckel’s research trip, see the letter from Ernst Haeckel, 19 October 1866 and n. 2.
CD refers to Haeckel’s Generelle Morphologie (Haeckel 1866).
See letter from Fritz Müller, 1 and 3 October 1866. CD included Müller’s estimate of the number of seeds in Maxillaria in Variation 2: 379, in ‘Fertilization of orchids’, p. 158 (Collected papers 2: 155), and in Orchids 2d ed., p. 278. In 1864, CD had received information from John Scott on the number of seeds in an Acropera capsule (see Correspondence vol. 12, letter from John Scott, 28 March 1864 and n. 9).
Müller had asked CD whether all species of Catasetum had upward projecting aerial roots (see letter from Fritz Müller, 1 and 3 October 1866; for a description of such roots and their function, see Dressler 1981, pp. 30, 90–2).
CD sent a copy of the fourth edition of Origin to Müller in August (see letter to Fritz Müller, 23 August [1866]). Müller received it in late October (see letter from Fritz Müller, [2 November 1866] and n. 14).


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–.

Cross and self fertilisation: The effects of cross and self fertilisation in the vegetable kingdom. By Charles Darwin. London: John Murray. 1876.

Dressler, Robert L. 1981. The orchids: natural history and classification. Cambridge, Mass., and London: Harvard University Press.

‘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.]

Forms of flowers: The different forms of flowers on plants of the same species. By Charles Darwin. London: John Murray. 1877.

Haeckel, Ernst. 1866. Generelle Morphologie der Organismen. Allgemeine Grundzüge der organischen Formen-Wissenschaft, mechanisch begründet durch die von Charles Darwin reformirte Descendenz-Theorie. 2 vols. Berlin: Georg Reimer.

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

Origin 4th ed.: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 4th edition, with additions and corrections. By Charles Darwin. London: John Murray. 1866.

Origin: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. By Charles Darwin. London: John Murray. 1859.

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


Hildebrand’s paper on trimorphism in Oxalis ["Über den Trimorphismus in der Gattung Oxalis", Monatsber. K. Preuss. Akad. Wiss. Berlin (1866): 352–74].

Problems of explaining brightly coloured, attractive seeds.

Haeckel has visited Down.

FM’s climbing plants paper is printed [J. Proc. Linn. Soc. Lond. (Bot.) 9 (1867): 344–9].

Letter details

Letter no.
Charles Robert Darwin
Johann Friedrich Theodor (Fritz) Müller
Sent from
Source of text
The British Library (Loan MS 10 no 10)
Physical description
LS(A) 6pp

Please cite as

Darwin Correspondence Project, “Letter no. 5261,” accessed on 13 July 2024,

Also published in The Correspondence of Charles Darwin, vol. 14