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Darwin Correspondence Project

To John Scott   12 April [1863]1

Down Bromley Kent

Ap. 12th

My dear Sir

I really hardly know how to thank you enough for your very interesting letter.2 I shall certainly use all the facts which you have given me (in a condensed form) on the sterility of orchids in the work which I am now slowly preparing for publication.—3 But why do you not publish these facts in a separate little paper? they seem to me well worth it, & you really ought to get your name known.4 I could equally well use them in my Book. I earnestly hope that you will experiment on Passiflora, & let me give your results.5

Dr. A. Grays observations were made loosely, he said in letter he would attend this summer further to the case, which clearly surprised him much.—6 I will say nothing about the Rostellum, stigmatic utriculi, fertility of Acropera & Catasetum, for I am completely bewildered:7 it will rest with you to settle these points by your excellent observations & experiments.— I must own I never could help doubting Dr. Hooker’s case of the Poppy.—8 You may like to hear what I have seen this morning: I found a Primrose plant with flowers having 3 pistils, which when pulled asunder without any tearing, allowed pollen to be placed on ovules. This I did with 3 flowers— pollen tubes did not protrude after several days. But this day, the sixteenth (N.B Primulas seem naturally slowly fertilised) I found many tubes protruded, & what is very odd they certainly seemed to have penetrated the coats of the ovules, but in no one instance the foramen of the ovule!!9 I mention this because it directly bears on your explanation of Dr. Cruger’s case.—10 I believe that your explanation is right; I shd. never have thought of it; yet this was stupid of me, for I remember thinking that the almost closed imperfect flowers of Viola & Oxalis were related to the protrusion of the pollen-tubes.11 My case of the Aceras with aborted labellum squeezed against stigma supports your view.—12 Dr. Cruger’s notion about the ants was a simple conjecture.—13 About crptogamic filaments rember Dr. C. says that the unopened flowers habitually set fruit—14

I think that you will change your view on the imperfect flowers of Viola & Oxalis;15 I am now making a few observations on them: last year I observed a few intermediate forms.—16

I have asked everywhere for seed of Campanula perfoliata.17 Can you get me any?

I am particularly obliged for your remark on Auriculas.—18

It seems to me a good experiment, that of preventing the orchid flowers opening.—19 What an excellent & indefatigable observer you are.

with sincere respect | Yours very faithfully | Ch. Darwin

P.S. Mr. Anderson sent me some seeds of the “abortive” Cattleya crispa; & not one in 100 or 200 contained even a trace of nucleus; the testa being quite empty.—20


The year is established by the relationship between this letter and the letter from John Scott, [1–11] April [1863].
CD wrote a draft of the section of Variation on ‘Crossing & Sterility’ between 1 April and 16 June 1863 (Variation 2: 85–191; see ‘Journal’ (Correspondence vol. 11, Appendix II)). Scott’s observations on self-sterility and cross-fertility in Oncidium and Maxillaria were briefly discussed in Variation 2: 133, 164.
Scott detailed his observations on self-sterility and cross-fertilisation in the orchid genus Oncidium in a paper read before the Botanical Society of Edinburgh on 14 May 1863 (Scott 1863a). See also Scott 1864b.
CD had been encouraging Scott to experiment on Passiflora since March 1863 (see letter to John Scott, 24 March [1863] and nn. 3 and 4). Scott later published his experiments on Passiflora in Scott 1864d. CD referred to Scott’s results in Variation 2: 137–8. See also Cross and self fertilisation, p. 330.
CD refers to Asa Gray’s observations of pollination in Gymnadenia tridentata (a synonym of Platanthera clavellata, the small green wood orchid), made in July and August 1862 (see Correspondence vol. 10, letters from Asa Gray, 29 July 1862 and 18–19 August 1862), and to the letter from Asa Gray, 22 September 1862 (ibid.). See letter from John Scott, [1–11] April [1863] and n. 13.
See letter from John Scott, [1–11] April [1863] and nn. 16–17. CD subsequently discussed Acropera and Catasetum in ‘Fertilization of orchids’, pp. 153–4 (Collected papers 2: 150–1); see also Orchids 2d ed., pp. 247–57, for mention of these genera, and for further discussion of the rostellum.
The reference is to an article by Joseph Dalton Hooker on the possibility of artificially pollinating flowers of the blue poppy without the involvement of the stigma (J. D. Hooker 1854a). See letter from John Scott, [1–11] April 1863 and n. 19.
See letter from John Scott, [1–11] April [1863] and n. 25. Hermann Crüger had observed the emission of pollen-tubes while the pollinia remained in situ in unopened flowers of Epidendreae (see letter from Hermann Crüger, 23 February 1863).
In Orchids, p. 324 n., CD described ‘monstrous’ flowers of Aceras in which pollen germinated and formed pollen tubes while still in the anther. See also letter to John Scott, 24 March [1863], and letter from John Scott, [1–11] April [1863].
See letter from John Scott, [1–11] April [1863]. In his letter to CD of 23 February 1863, Crüger had suggested that the protrusion of pollen-tubes that he had observed in Epidendreae (see n. 10, above) was due to ants carrying stigmatic fluid to the pollen. See also letter to John Scott, 24 March [1863].
Scott had suggested (see letter from John Scott, [1–11] April [1863]) that the pollen-tubes described by Crüger as occurring in unopened orchid flowers (see letter to Journal of Horticulture, [17–24 March 1863]) could be fungal filaments; Scott had observed such filaments in the flowers of Bletia, initially mistaking them for pollen-tubes.
As he explained in his letter of [1–11] April [1863], Scott believed that the germination of pollen-grains in situ in cleistogamic flowers, like those of the imperfect forms of Viola and Oxalis, was a ‘purely accidental occurrence, having no ultimate import in the economy ⁠⟨⁠of⁠⟩⁠ the spec⁠⟨⁠ies⁠⟩⁠’. For CD’s study of the flowers, see n. 16, below, and letter to Journal of Horticulture, [17–24 March 1863] and n. 7. See also letter to Asa Gray, 31 May [1863].
For CD’s observations of Viola and Oxalis in March and April 1863, see DAR 111: 6, 10, and 45. For CD’s observations and experiments on the two genera in 1862, see Correspondence vol. 10. CD’s published observations on cleistogamic flowers in these genera are in Forms of flowers, pp. 314–24.
See letter to Asa Gray, 20 March [1863] and n. 5. For CD’s notes on the genus, see DAR 111: 29–32.
Scott had forwarded information to CD regarding the inheritance of style length in Primula auricula (see letter from John Scott, [1–11] April [1863]).
To investigate the cause of self-fertilisation in flowers that did not open, Scott had suggested cementing together the perianths of ‘perfect’ flowers shortly before their expansion (see letter from John Scott, [1–11] April [1863]).


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.

‘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.

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.

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


Encourages JS to publish on sterility of orchids and to experiment on Passiflora.

Doubted Hooker’s poppy case.

Describes case of primrose with three pistils: when pulled apart allowed pollen to be placed directly on ovules. This supports JS’s explanation of H. Crüger’s case.

Letter details

Letter no.
Charles Robert Darwin
John Scott
Sent from
Source of text
DAR 93: B59, B77–8
Physical description
ALS 6pp

Please cite as

Darwin Correspondence Project, “Letter no. 4084,” accessed on 19 April 2024,

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