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Darwin Correspondence Project

From George Bentham   10 July 1864

25, Wilton Place, | S.W.

July 10/64

My dear Darwin

I enclose flowers of the two forms of two species of Ægiphila1 (Verbenaceæ never referred by me to Labiatæ)2 the long stamened marked ♂ the short stamened ♀—the two forms always on different specimens and often made two species of although admitted to differ in no other particular   Thus the long and short stamened Æ mollis are both figured by H. B. K. the former as Æ Mutisia, the latter as Æ mollis3

I have often observed long and short stamened forms of different plants as I believe I have frequently mentioned to you4 and the circumstance is so generally familiar that I do not well recollect precise instances where it is or is not. In Trichonemas which I suppose you could get seeds or bulbs of from any friends in Italy or other Mediterranean countries I have often observed it and it is (as I said in the article) made a specific character5   I believe there is something of the same kind in the allied genus Crocus. There are great differences in the styles and stamens in some species of Boronia as well as I could make out from dried specimens— especially I soaked a considerable number of the pinnata (Bth Fl. Austral. 1. 318)6 which is I believe in our gardens. Long and short stamens and styles occur I believe in several Pavettas Stylocorynas and other Rubiaceæ which A Gray also has somewhere pointed out.—7 There is a dimorphism in many Veronicas though I do not know whether it extends beyond the size & colour of the flowers   Many species have a form with larger blue, and another with smaller more pinkish flowers which have on that account alone been made two species of as V. fruticulosa. I have also seen it in V. teucrium, V. chamædrys and others.

I have just been doing the Australian Droseras8 where the forms of style are infinitely varied but generally constant in the same species—and yet there is something farther to learn for in a few cases species can only or almost only be distinguished by the style as in D. Burmanni & D. spathulata D. filicaulis and D. Menziesii, D. penicilloris and D. Huegelii.— Unfortunately I cannot have so many flowers at command to examine as I could of Boronia and they are very difficult to examine dry. Another character in some species is unaccompanied by other distinctions   that is the seed either linear with the nucleus occupying the middle only or ovoid the testa not produced beyond the nucleus as between D. peltata & D. auriculata— these characters are also relied on for our own Droseras which are I believe otherwise good species.

Yours ever sincerely | George Bentham

CD annotations

On cover: ‘Trichonemas | Boronia pinnata | Rubiaceæ | Veronicas with 2 flower | V. teucrium | [V.] chamædrys’ ink; ‘Verbenaceæ— dimorphic??’ ink; ‘Ægiphila specimen’ pencil


See letter to George Bentham, 7 July [1864]. CD describes the flowers of Aegiphila elata and A. mollis, which were sent by Bentham, in Forms of flowers, pp. 123–4.
The reference is to Alexander von Humboldt, Aimé Bonpland, and Karl Sigismund Kunth, Nova genera et species plantarum (Humboldt et al. 1815–25), volume 2, figures 130 and 131.
Bentham 1864b, pp. 380–1. See letter to George Bentham, 7 July [1864], n. 2.
The description of Boronia pinnata appears in the first volume of Bentham’s Flora Australiensis, which was published in 1863 (see Bentham 1863–78, 1: 318–19).
Bentham probably refers to Asa Gray’s remark in his Manual of botany that several genera of Rubiaceae have flowers of two sorts, one with long stamens and short styles, the other with short stamens and long styles. Gray termed these plants ‘diœciously dimorphous’ (see Gray 1856, p. 171 n.). In 1861, Gray had referred CD to the Rubiaceae because of their dimorphic flowers (see Correspondence vol. 9, letters from Asa Gray, [27 and 29 August] and 2 September [1861], and 11 October 1861). See also Correspondence vol. 10, letter from Asa Gray, [2 June 1862] and n. 2. CD discussed the Rubiaceae in Forms of flowers, pp. 284–6.
The description of Drosera appears in the second volume of Bentham’s Flora Australiensis, which was published in 1864 (see Bentham 1863–78, 2: 452–69).


Bentham, George and Mueller, Ferdinand von. 1863–78. Flora Australiensis: a description of the plants of the Australian territory. 7 vols. London: Lovell Reeve and Company.

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.


Sends specimens of two species of Aegiphila [see Forms of flowers, p. 123]. Discusses similar forms in other plants.

Letter details

Letter no.
George Bentham
Charles Robert Darwin
Sent from
London, Wilton Place, 25
Source of text
DAR 110: B107–9
Physical description
4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 4556,” accessed on 15 January 2021,

Also published in The Correspondence of Charles Darwin, vol. 12