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Darwin Correspondence Project

To John Scott   24 March [1863]1

Down Bromley Kent.

March 24th

Dear Sir

Your letter, as every one you have written, has greatly interested me.2 If you can show that certain individual Passifloras, under certain known or unknown conditions of life, have stigmas capable of fertilisation by pollen from another species, or from another individual of its own species, yet not by its own individual pollen, (its own individual pollen being proved to be good by its action on some other species) you will add a case of great interest to me; & which in my opinion would be quite worth your publication. I always imagined that such recorded cases must be due to unnatural conditions of life; & think I said so in Origin.3 I am not sure that I understand your result, whether it means what I have above obscurely expressed. If you can prove the above, do publish; but if you will not publish I earnestly beg you to let me have the facts in detail; but you ought to publish for I may not use facts for years.—4

I have been much interested by what you say on the Rostellum exciting pollen to protrude tubes;5 but are you sure that the rostellum does excite them? would not tubes protrude if placed on part of column or base of petals &c., near to the stigma?— Please look at Cottage Gardener (or J. of Hort) to be published tomorrow week for letter of mine, in which I venture to quote you, & in which you will see curious fact about unopened orchid flowers setting seed in W. Indies.6 Dr. Cruger attributes protrusion of tubes, to ants carrying stigmatic secretion to pollen; but this is mere hypothesis.7 Remember pollen-tubes protrude within anther in Neottia nidus-avis—8 I did think it possible or probable that perfect fertilisation might have been effected through rostellum.

What a curious case your Gongora must be:9 could you spare me one of largest capsule: I want to estimate number of seed, & try my hand if I can make them grow. This, however, is foolish attempt; for Dr. Hooker who was here a day or two ago;10 says they cannot at Calcutta, & yet imported species have seeded & have naturally spread on to the adjoining trees!

Dr. Cruger thinks I am wrong about Catasetum; but I cannot understand his letter:11 he admits there are 3 forms in 2 species; & he speaks as if the sexes were separate in some & that others were hermaphrodite; but I cannot understand what he means.— He has seen lots of great Humble-bees buzzing about the flowers with the pollinia sticking to their backs! Happy man!!. I have the promise but not yet surety of some curious results with my homorphic seedling Cowslips: these have not followed rule of Chinese Primula; homorphic seedlings from short-styled parent have presented both forms, which disgusts me.—12

You will see that I am better; but still greatly fear that I must have compulsory holiday.

With sincere thanks & hearty admiration at your powers of observation.— Dear Sir | Yours sincerely | C. Darwin

My poor P. Scotica, look very sick, which you so kindly sent me.—13


The year is established by the reference to the letter from John Scott, 21 March [1863].
Following a discussion of genera, including Passiflora, in which some species had been found to be more easily fertilised by the pollen of another species than their own pollen (Origin, p. 251), CD wrote: Although the plants in these experiments appeared perfectly healthy, and although both the ovules and pollen of the same flower were perfectly good with respect to other species, yet as they were functionally imperfect in their mutual self-action, we must infer that the plants were in an unnatural state.
Scott published the results of his experiments on Passiflora in Scott 1864d; CD cited Scott’s paper in Variation 2: 137. Although CD wrote drafts of the chapters on inheritance for Variation (Variation 2: 1–84) between 23 January and 1 April 1863 (see ‘Journal’ (Correspondence vol. 11, Appendix II)), the work was not published until 1868.
See letter to Journal of Horticulture and Cottage Gardener, [17–24 March 1863].
See Orchids p. 324 n.
Joseph Dalton Hooker visited Down House on 22 March 1863 (see letter from J. D. Hooker, [24 March 1863]).
CD refers to seedlings raised from crossing experiments with cowslips (Primula veris) carried out in 1862 (see DAR 157a: 77 and DAR 108: 70; see also Correspondence vol. 10). These experiments are described in ‘Illegitimate offspring of dimorphic and trimorphic plants’, pp. 423–30, where CD notes that the ‘short-styled form of the cowslip, when self-fertilized, does not transmit the same form nearly so truly as does that of P. sinensis.’ With a single exception, CD had found that both long- and short-styled plants of P. sinensis (the Chinese primrose), produced only own-form plants when pollinated with own-form pollen (see letter to John Scott, 20 [February 1863]).
Scott had sent CD specimens of Primula scotica in January (see letter from John Scott, 6 January 1863).


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

‘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.

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.

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.


Enthusiastic about JS’s work on Passiflora self-incompatibility.

CD quotes JS on rostellar pollen germination [in "Fertilisation of orchids", Collected papers 2: 77–8]. H. Crüger attributes it to ants’ carrying stigmatic secretion to pollen.

Homomorphic cowslip seedlings are, sadly, showing variation.

Letter details

Letter no.
Charles Robert Darwin
John Scott
Sent from
Source of text
DAR 93: B72–4
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 4060,” accessed on 20 January 2022,

Also published in The Correspondence of Charles Darwin, vol. 11