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Darwin Correspondence Project

To Asa Gray   4 December 1876

Down, | Beckenham, Kent. | Railway Station | Orpington. S.E.R.

Dec 4. 1876

My dear Gray,

I think I told you that I was going to re-publish my Dimorphic papers, with additions   I have become convinced that plants of this class cannot be recognized merely by the varying lengths of pistils & stamens in a few specimens. It is necessary to compare size of pollen grains & state of stigma.1  Therefore I want you much to send me one or two flowers of both forms of Leucosmia & Drymispermum, (mentioned in Amer: Journ of Science Vol 39 p 104—) if not very rare & precious.2 The flowers ought to be rather youngish ones otherwise the pollen will have been shed or lost. My object is to see plants in as many natural families as possible, and if you could spare me flowers of any dimorphic plant, not included in the Primulaceæ, Lineae Oxalidæ, Gentianeæ, Verbenaceæ, Boragineæ, Rubiaceae & Lythraceæ, I should be very much obliged.3

One other question, do any of the dimorphic plants known to you inhabit water or marshes?4 I hope & suppose that you have assistants whom you could direc〈t〉 to look out for the desired specimens.

My dear Gray | Yours ever sincerely | Charles Darwin


CD incorporated the material from his earlier papers on dimorphic and trimorphic plants (‘Dimorphic condition in Primula’, ‘Three sexual forms of Catasetum tridentatum’, ‘Two forms in species of Linum, ‘Three forms of Lythrum salicaria’, ‘Illegitimate offspring of dimorphic and trimorphic plants’, and ‘Specific difference in Primula’) into a broader framework in Forms of flowers, published in July 1877 (Freeman 1977). On p. 2, he said that he now preferred Friedrich Hildebrand’s term ‘heterostyled’ to describe plants with two or three different forms adapted for reciprocal fertilisation. After a discussion of the difficulties in identifying them, CD remarked, ‘when the pistils and stamens differ in length in two or three sets of individuals, and this is accompanied by a difference in the size of the pollen-grains or in the state of the stigma, we may infer with much safety that the species is heterostyled’ (ibid., p. 3). For CD’s conclusions about the nature of heterostyly, see ibid., pp. 244–77.
Gray’s review in the American Journal of Science and Arts (Gray 1865a, p. 104) of John Scott’s ‘Observations on the functions and structure of the reproductive organs in the Primulaceae’ (Scott 1864b) states that the genera Leucosmia and Drymispermum probably exhibit long- and short-styled forms. CD had previously asked about other cases of dimorphism in his letter to Asa Gray, 19 April [1865] (Correspondence vol. 13). He discussed these genera in Forms of flowers, pp. 114–15.
CD uses the names of the natural orders (families) as given in J. Lindley 1853. These are roughly equivalent to the modern families Primulaceae (primrose), Linaceae (flax), Oxalidaceae (wood sorrel), Gentianaceae (gentian), Verbenaceae (verbena), Boraginaceae (borage or forget-me-not), Rubiaceae (coffee or madder), and Lythraceae (loosestrife). CD discussed species from these families in Forms of flowers.
CD featured the marsh-dwelling plant Menyanthes trifoliata, which was already known to him, in the section on dimorphic plants in Forms of flowers, p. 115. He discussed what proportion of genera were aquatic in heterostyled plants, hermaphrodite plants, and plants that had the sexes separate in ibid., p. 257 n.


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

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

Freeman, Richard Broke. 1977. The works of Charles Darwin: an annotated bibliographical handlist. 2d edition. Folkestone, Kent: William Dawson & Sons. Hamden, Conn.: Archon Books, Shoe String Press.

‘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.

Lindley, John. 1853. The vegetable kingdom; or, the structure, classification, and uses of plants, illustrated upon the natural system. 3d edition with corrections and additional genera. London: Bradbury & Evans.

‘Two forms in species of Linum’: On the existence of two forms, and on their reciprocal sexual relation, in several species of the genus Linum. By Charles Darwin. [Read 5 February 1863.] Journal of the Proceedings of the Linnean Society (Botany) 7 (1864): 69–83. [Collected papers 2: 93–105.]


Plans to republish his paper on dimorphism with additions [Forms of flowers]. Is convinced it is necessary to compare pollen-grains and the state of the stigma to recognise dimorphic plants. Requests specific plants to test for dimorphism and would welcome examples from any family in which he has not encountered dimorphic species.

Letter details

Letter no.
Charles Robert Darwin
Asa Gray
Sent from
Source of text
Archives of the Gray Herbarium of Harvard University (115)
Physical description
3pp †

Please cite as

Darwin Correspondence Project, “Letter no. 10697,” accessed on 7 May 2021,

Also published in The Correspondence of Charles Darwin, vol. 24