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Darwin Correspondence Project

From Asa Gray   5 December 1876

Herbarium of Harvard University, | Botanic Garden, Cambridge, Mass.

Dec. 5 1876

Dear Darwin

Your postal of 20th Nov. received.1

I know nothing about the Indian species of Hottonia. Somebody saying (I can’t at this moment tell who*) that H. palustris is dimorphous; I thought I had it clear that our H. inflata was too—but only from dried specimens. (I have not for years seen it growing. I must get it & have it looked to.) I fear I judged so hastily from finding some young fruit tipped with extremely short style, others with style of fair length, but, as you know, short indeed compared with either form of H. palustris.— But now, on looking out various flowers, I see it must be, as you say, not structurally dimorphic.2 And turning to a forgotten observation of dear old Torrey I see what misled me.3

I have Torrey’s note—the essential part of it copied for you. The subsessile stigmas must have belonged to cleistogenous flowers.

Torrey cannot mean of course—that all the flowers of H. inflata are cleistogenous,—only some of the earlier ones. All the later ones at least open out their well-formed corolla, &c—

Curious that one species should take pains to close-fertilize some flowers—the other to cross all. ⁠⟨⁠15 lines excised⁠⟩⁠

Now I want to beg of you to consider about a name for this kind of thing,—on which, as a good judge, you could Bentham,—or indeed, Hooker,4 if he can give it attention.—

This matter will need to come into generic or specific ⁠⟨⁠15 lines excised⁠⟩⁠

characters, and therefore wants a terse and unambiguous mode of expression in a single word.

My old expression 30 or so years ago diœcio-dimorphous—you reasonably objected to implying separation of sexes (which tho’ it need not.) Yours of dimorphous should be, as the lawyers say void for vagueness, there being plenty of other kinds of dimorphism in flowers.

Hildebrands, of heterostylous—the difference being in other things as well as style, and, I think, possible sometimes not in the style. The term will not work well in characters, whether Latin or English.— I have proposed, accordingly—in a little article not yet published—to use the term heterogone in other forms heterogonous in Latin Flores heterogoni, with the counterpart homogone, homogonous, Flores homogoni.

This means, you see, explicitly, diverse genitalia, and the [G[goni,i]G] is used as in the common botanical term perigonium.5 I wish you would adopt this. I am very glad you will re-edit & collect those papers.

Yours ever, | A. Gray

*Oh yes, I now have Scott’s & your paper before me!6


Bulletin of the Torrey Botanical Club, vol. II. 22—June 1871.7

“Note on Hottonia inflata, Ell.

xxx About three weeks ago xx it was just commencing to throw up its scapes, in which state I received a number of specimens & placed them in a glass vase of water, so that I had an opportunity of watching their development in my study. The scapes have grown to the height of 4 or 5 inches, & have produced numerous whorls of flowers. Their corolla is scarcely more than a line and a half in length, & its border never expands. At a very early age, when the flower buds are barely formed, fertilization takes place, & the corolla is detached from its base by the enlargement of the ovary, on the summit of which it remains, like a little cap, until the fruit is mature. Fertilization must take place without any aid from without, for the corolla does not open, the stamens & pistil being closely shut in, and the anthers being directly in contact with the stigma. xxx

John Torrey

Columbia College | New York—June 6, 1871.”


The postcard has not been found.
Hottonia palustris is the water violet; H. inflata is American featherfoil. Gray used the terms dimorphous and cleistogenous instead of dimorphic and cleistogamic. CD had made the distinction between structural and functional dimorphism in ‘Two forms in species of Linum, p. 82. Plants with observable differences in the form of the flower were considered structurally dimorphic. He clarified his use of the phrase ‘dimorphic in function’ as referring to plants that could be ‘divided into two equal bodies functionally but not structurally different’ in his letter to Fritz Müller, 25 September [1866] (Correspondence vol. 14).
CD cited the observations of John Torrey on Hottonia inflata (Torrey 1871) as evidence that the species produced cleistogamic flowers in Forms of flowers, pp. 53 and 313; see n. 7, below.
Gray coined the term ‘diœcio-dimorphous’ in Torrey and Gray 1838–43, 2: 38, and applied it to several genera in the family Rubiaceae in his ‘Dimorphism in the genitalia of flowers’ (Gray 1862d, p. 419). CD objected to the term as used by Gray in Gray 1862d in his letter to Asa Gray, 26[–7] November [1862] (Correspondence vol. 10), and in his paper, ‘Two forms in species of Linum, p. 83 (Collected papers 2: 105). In Forms of flowers, p. 2, CD explained that he had given up his old terminology of dimorphic and trimorphic to describe plants with ‘two or three forms, differing in the length of their pistils and stamens and in other respects’, and adopted Friedrich Hildebrand’s term ‘heterostyled’. On p. 2 n., he added that the term did not express all the differences between the forms but that he would not adopt Gray’s term ‘heterogone’ or ‘heterogonous’ (described in Gray 1877) because ‘heterostyled’ had been adopted by writers in various countries.
In his paper on dimorphism in the Primulaceae (Scott 1864b, pp. 78–9), John Scott quoted CD’s notes on Hottonia palustris sent with CD’s letter to him of 2 July [1863] (Correspondence vol. 11). Gray also refers to CD’s paper ‘Dimorphic condition in Primula. In Forms of flowers pp. 52–3, CD cited Herman Müller’s experiments on Hottonia palustris, which were much fuller than his own had been.
The extract is copied from Torrey 1871 with minor differences from the original. In Forms of flowers, p. 53, CD cited these observations to support his claim that Hottonia inflata did not appear to be heterostyled, but was ‘remarkable from producing cleistogamic flowers’.


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–.

‘Dimorphic condition in Primula’: On the two forms, or dimorphic condition, in the species of Primula, and on their remarkable sexual relations. By Charles Darwin. [Read 21 November 1861.] Journal of the Proceedings of the Linnean Society (Botany) 6 (1862): 77–96. [Collected papers 2: 45–63.]

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

Torrey, John. 1871. Note on Hottonia inflata, Ell. Bulletin of the Torrey Botanical Club 2: 22.

‘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.]


Dimorphism and cleistogamy in Hottonia.

AG wants new, unambiguous term for what is now referred to as "dimorphism", "dioecio-dimorphism", or "heterostyly"; proposes "heterogone".

Sends an excerpt from Bulletin of Torrey Botanical Club 2 (June 1871) on Hottonia inflata.

Letter details

Letter no.
Asa Gray
Charles Robert Darwin
Sent from
Herbarium of Harvard
Source of text
DAR 165: 192, DAR 111: A92
Physical description
ALS 5pp inc, encl 2pp

Please cite as

Darwin Correspondence Project, “Letter no. 10699,” accessed on 7 June 2023,

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