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Darwin Correspondence Project

To Alphonse de Candolle   17 June [1862]

Down. | Bromley. | Kent. S.E.

June 17th

My dear Sir

I am extremely much obliged for your kind & very interesting letter.1 I am pleased that you are interested by the Primula case. Your questions & remarks show that you have gone to the root of the matter. I am now trying various analogous experiments on several plants & on the seedlings raised from the so-called heteromorphic & homomorphic unions; & the results (as far as I have yet seen; for the capsules are gathered, but not yet examined) are interesting; Whenever I publish I will do myself the pleasure of sending you a copy.2 I am particularly obliged for your information on Alkanna. I have examined the small imperfect flowers of Viola & Oxalis: the case is very different both functionally & structurally from that of Primula.—3

You kindly enquire about my larger work; it does make progress, but very slowly owing to my own weak health & ill-health in my family.4 I have, also, been seduced to publish a small work on the Fertilisation of Orchids, which has taken up nearly ten months. As Mr Bentham & Asa Gray think well of this Book, I have sent by this post a copy for you.5 One main object has been to show how wonderfully perfect the structure of plants is; another regards close breeding in & in, to which I see you have attended.— I am not at all surprised that you are not willing to admit natural selection: the subject hardly admits of direct proof or evidence.6 It will be believed in only by those who think that it connects & partly explains several large classes of facts: in the same way opticians admit the undulatory theory of light, though no one can prove the existence of ether or its undulations.—

I hope you will publish on Quercus, & I shall be most grateful for a copy; the genus has long appeared to me preeminently interesting under the point of view to which you refer.7 I am, also, rejoiced to hear that you have the intention of again returning to Geographical Distribn. I believe few, or no one, can have read your truly great work with more care than I have;8 & no one can feel more respect & admiration for it & its author.—

Pray believe me, my dear Sir | Yours sincerely & respectfully | Ch. Darwin


In January and February 1862, CD carried out crossing experiments with Primula sinensis using plants raised the previous year from the seed produced by homomorphic and heteromorphic crosses (see letters to J. D. Hooker, 7 March [1862] and n. 10, and 23 June [1862] and n. 4). (By ‘homomorphic unions’, CD meant crosses in which fertilisation was effected by own-form pollen; by ‘heteromorphic unions’, those in which it was effected by different-form pollen.) In April and May, he performed experiments on the common cowslip, P. veris, not only repeating the homomorphic and heteromorphic crosses that he had carried out in 1860 and 1861 (see letter to J. D. Hooker, 23 June [1862] and n. 4), but also investigating the possible prepotency of different-form pollen from a polyanthus (which he considered a variety of the same species) over own-form pollen from a cowslip (see CD’s notes from these experiments in DAR 157a: 76–7 and DAR 108: 70). Some of the results of CD’s experiments with P. sinensis are recorded in ‘Illegitimate offspring of dimorphic and trimorphic plants’ (a paper not included in Collected papers), which was published in 1869; the results of his experiments with P. veris are recorded in Cross and self fertilisation, p. 28, and ‘Three forms of Lythrum salicaria, p. 189 (see also Collected papers 2: 121–2). In the letter, CD interlined the phrase ‘on several plants &’ (see Manuscript alterations and comments); he was engaged in crossing experiments with several members of the Melastomataceae, which he believed might exhibit dimorphism (see, for example, letter to George Bentham, 3 February [1862], letters to J. D. Hooker, 9 February [1862], 15 [May 1862], and 30 May [1862], and letters to Asa Gray, 15 March [1862] and 10–20 June [1862]).
See letter from Alphonse de Candolle, 13 June 1862 and n. 5. CD and many of his household had had influenza early in the year (see letter to J. D. Hooker, 16 January [1862], and letter to Asa Gray, 22 January [1862]). Horace Darwin became ill during January and had suffered bouts of ill health ever since (see letter to W. E. Darwin, 14 February [1862]). On 12 June, Leonard Darwin was sent home from school suffering from scarlet fever (see letter to W. E. Darwin, 13 [June 1862]). In his ‘Journal’ (see Correspondence vol. 10, Appendix II), CD recorded: ‘Much time wasted June & July from Leonard’s illness’.
See letter from George Bentham, 15 May 1862, and letter from Asa Gray, 18 May 1862. See also letter from J. D. Hooker, [17 May 1862], and letter to Asa Gray, 10–20 June [1862]. Candolle’s name is included on CD’s presentation list for Orchids (see Correspondence vol. 10, Appendix IV).
A. de Candolle 1855. There is an annotated copy of this work in the Darwin Library–CUL (see Marginalia 1: 106).


Candolle, Alphonse de. 1855. Géographie botanique raisonnée ou exposition des faits principaux et des lois concernant la distribution géographique des plantes de l’époque actuelle. 2 vols. Paris: Victor Mason. Geneva: J. Kessmann.

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.

‘Illegitimate offspring of dimorphic and trimorphic plants’: On the character and hybrid-like nature of the offspring from the illegitimate unions of dimorphic and trimorphic plants. By Charles Darwin. [Read 20 February 1868.] Journal of the Linnean Society of London (Botany) 10 (1869): 393–437.

Marginalia: Charles Darwin’s marginalia. Edited by Mario A. Di Gregorio with the assistance of Nicholas W. Gill. Vol. 1. New York and London: Garland Publishing. 1990.

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.

‘Three forms of Lythrum salicaria’: On the sexual relations of the three forms of Lythrum salicaria. By Charles Darwin. [Read 16 June 1864.] Journal of the Linnean Society (Botany) 8 (1865): 169–96. [Collected papers 2: 106–31.]


Is pleased that AdeC is interested in the Primula case ["Dimorphic condition of Primula", Collected papers 2: 45–63]. Is pursuing analogous experiments on other plants and on seedlings raised from the unions.

CD’s "large work" progresses slowly owing to ill health and his work on Orchids.

CD is not surprised that AdeC is unwilling to admit natural selection – "the subject hardly admits of direct proof or evidence. It will be believed in only by those who think that it connects & partly explains several large classes of facts".

Hopes AdeC will publish on Quercus

and rejoices that he intends to return to the study of geographical distribution. No one can claim to have read AdeC’s truly great work on that subject [Géographie botanique (1855)] with more care than CD.

Letter details

Letter no.
Charles Robert Darwin
Alphonse de Candolle
Sent from
Source of text
Archives de la famille de Candolle (private collection)
Physical description
ALS 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 3608,” accessed on 25 July 2024,

Also published in The Correspondence of Charles Darwin, vol. 10