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Darwin Correspondence Project

To George Bentham   7 July [1864]1

Down Bromley | Kent.

July 7

Dear Bentham

In the last Nat. Hist Review there is an interesting article which must be by you, in which you say that Trichonema & some other plants present 2 forms.2 I shd be particularly obliged if you cd give me the names of these plants; for then perhaps I cd get seed. For instance, you told me of Oxalis & I wrote to the Cape & have got about 20 species some of which are grandly Dimorphic.3 I know that I exaggerate the interest of whatever I am about, but the Lythrum case seems to me so surprising that I wish to pursue the subject.4 In yr Oxalis letter you say that Ægiphila is dimorphic;5 now I have no idea whether the species are rare or whether it wd cause much trouble to send me a dried flower of the 2 forms of any species. If it does not give much trouble I shd much like to see whether they are really dimorphic like Primula &c or like Thyme which latter is a very different case.6 I believe that you told me that this genus is a Labiate,7 but Lindley makes it one of the Verbenaciæ.8 I know how busy you are but I trust to your kindness to forgive me for troubling you—

Believe me dear Bentham | yours very sincerely | Ch. Darwin


The year is established by the reference to Bentham 1864b (see n. 2, below).
In his unsigned review ‘South-European Floras’, which appeared in the July 1864 issue of Natural History Review, pp. 369–84, Bentham noted that certain species of Trichonema and some other plants that were distinguished by the comparative lengths of their styles and stamens were probably dimorphic forms, rather than different species (Bentham 1864b, pp. 380–1). CD annotated the review in his unbound copy of the July 1864 issue in the Darwin Library–CUL. CD had been carrying out extensive research on dimorphism since 1861 (see Correspondence vols. 9–11).
See letter from George Bentham, 29 November 1861 (Correspondence vol. 9). CD received Oxalis specimens from Roland Trimen in 1863, and Oxalis bulbs in May 1864 (see Correspondence vol. 11, letter from Roland Trimen, 10, 13, and 18 October 1863, and this volume, letter to Roland Trimen, 13 May 1864).
CD’s paper ‘Three forms of Lythrum salicaria had been read at the Linnean Society, of which Bentham was president, on 16 June 1864.
Bentham noted the dimorphic character of Aegiphila in his letter of 26 November 1861 (Correspondence vol. 9). CD cited this information in ‘Dimorphic condition in Primula, p. 62.
CD discussed the differences between Thymus and Primula in his letter to George Bentham, 30 November [1861] (Correspondence vol. 9); he believed that Thymus was gyno-dioecious (see letter to W. E. Darwin, 14 May [1864] and nn. 8, 11, and 14).
CD had referred to the genus Aegiphila as a member of the family Labiatae in ‘Dimorphic condition of Primula’, p. 62; he had evidently misunderstood Bentham’s references to Mentha, Thymus, and the ‘ægiphilos’ (see CD’s annotation to the letter from George Bentham, 26 November 1861 (Correspondence vol. 9)). See letter from George Bentham, 10 July 1864.
In John Lindley’s Vegetable kingdom, 3d ed., Aegiphila is classed among the Verbenaceae (Lindley 1853, p. 664).


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 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.]

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.

‘Three forms of Lythrum salicaria’: On the sexual relations of the three forms of Lythrum salicaria. By Charles Darwin. [Read 16 June 1864.] Journal of the Linnean Society (Botany) 8 (1865): 169–96. [Collected papers 2: 106–31.]


Asks for names of plants mentioned in an article in Natural History Review ["South European Floras", n.s. 4 (1864): 369–84] so he can get seeds.

Also would like specimens of the two forms of Aegiphila.

Letter details

Letter no.
Charles Robert Darwin
George Bentham
Sent from
Source of text
Royal Botanic Gardens, Kew (Bentham Correspondence, Vol. 3, Daintree–Dyer, 1830–1884, GEB/1/3: f. 716)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 4554,” accessed on 7 March 2021,

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