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Darwin Correspondence Project

To Asa Gray   9 August [1862]1

Down Bromley Kent

Aug 9th

My dear Gray.—

It is late at night & I am going to write briefly & of course to beg a favour. But first let me thank you most cordially for the stamps in letter of July 21, of superlative value to my Boy, who has gloated over them once.—2 We hope in bed-carriage to get him to sea on Wednesday next.—3

I have settled with Trübner; I presume he spoke to Murray for he has charged me reduced price 6s .8d, instead of 9s.).—4 If you have spare copy pray present one from me to your pupil (Rosback?)5

The Mitchella very good, but pollen apparently equal-sized.6 I have just examined Hottonia   grand difference in pollen.—7 Echium vulgare a humbug, merely case like Thymus.8 But I am almost stark staring mad over Lythrum; if I can prove what I fully believe, it is grand case of Trimorphism with 3 different pollens & 3 stigmas; I have castrated & fertilised above 90 flowers, trying all 18 distinct crosses which are possible within limits of this one species! I cannot explain, but I feel sure you would think it grand case.—9

I have been writing to Botanists to see if I possibly can get L. hyssopifolia,10 & it has just flashed on me that you might have Lythrum in N. America.—& I have looked to your manual11    For the love of Heaven have a look at some of your species, & if you can get me seed, do; I want much to try species with few stamens, if they are dimorphic: Nesæa verticillata I shd expect to be trimorphic.12 Seed! Seed! Seed!

I shd. rather like seed of Mitchella— But oh Lythrum!—

Your utterly mad friend | C. Darwin

There is reason in my madness, for I can see that to those who already believe in change of species, these facts will modify to certain extent whole view of Hybridity— Homomorphic grandchildren (from two homorphic unions) of Primula are become more sterile.—13


The year is established by the relationship to the letter from Asa Gray, 21 July 1862.
Gray had enclosed some American postage stamps for Leonard Darwin with the letter from Asa Gray, 21 July 1862.
According to Emma Darwin’s diary (DAR 242), the Darwins travelled to Southampton on 13 August 1862. Before they could continue their journey to Bournemouth, however, Leonard suffered a ‘slight relapse’ in his recovery from scarlet fever, and Emma contracted the disease (see letter to A. R. Wallace, 20 August [1862]); consequently they spent the remainder of August in Southampton, moving on to Bournemouth in September (see ‘Journal’ (Correspondence vol. 10, Appendix II)). Emma discussed details of the holiday plans in a letter to William Erasmus Darwin, [9 August 1862] (DAR 219.1: 61).
Gray had asked CD to arrange for six copies of Orchids to be sent to him by the London bookseller and publisher Nicholas Trübner (see letter to Nicholas Trübner, 23 June [1862]). In the letter from Asa Gray, 21 July 1862, Gray mentioned having received an invoice for the copies, and stated that it would be wrong for CD to pay the retail price for them, since he supposed CD’s publisher, John Murray, would supply him with copies at half price. CD’s Account book–cash accounts (Down House MS) records a payment of £2 1s. to Trübner on 3 August 1862.
Joseph Trimble Rothrock had offered to provide CD with information on Houstonia (see letters from Asa Gray, 2–3 July and 15 July [1862]). CD had not yet received Rothrock’s observations, detailed in the letter from Asa Gray, 4 August 1862.
Gray had sent with his letter to CD of 15 July [1862], specimens of Mitchella repens to examine for heterostyly.
No previous correspondence with Gray on Echium vulgare has been found. However, in Forms of flowers, p. 111, CD reported that ‘from statements made by Vaucher [Vaucher 1841, 3: 461]’, he had thought at first that this species was heterostyled, but had soon seen his error. Later in the volume (pp. 305–6), CD described the existence of two forms of flower in this species, namely, an ordinary hermaphrodite form and a female form. CD had already observed this phenomenon in Thymus (see Correspondence vol. 9, letter to George Bentham, 30 November [1861], and letter to Asa Gray, 11 December [1861]; see also this volume, letter to Daniel Oliver, 12 [April 1862]).
CD had told Gray of his interest in the occurrence of trimorphism in Lythrum salicaria in the letters to Asa Gray, 1 July [1862] and 28 July [1862]. There are a number of notes in DAR 27.2 (ser. 2), recording the details of crossing experiments carried out by CD on this species in the summer of 1862; the earliest is dated 31 July 1862 (DAR 27.2 (ser. 2): 7). CD’s paper on the subject (‘Three forms of Lythrum salicaria) was read before the Linnean Society of London on 16 June 1864.
A. Gray 1856. There is an annotated copy of this work in the Darwin Library–CUL (see Marginalia 1: 348–51).
Nesaea, like Lythrum, is a member of the Lythraceae.
In January and February 1862, CD carried out crossing experiments on plants of Primula sinensis raised from the seed produced by similar crosses made in 1861 (see letter to J. D. Hooker, 23 June [1862] and n. 4). He crossed the offspring of the homomorphic crosses (i.e., those in which long- or short-styled parents were fertilised from own-form pollen) both homomorphically and heteromorphically, confirming his expectation that they would be sterile, and crossed the offspring of the heteromorphic crosses ‘for comparison … as these would of course be fully fertile’ (DAR 108: 35). CD made notes on the rates of growth and health of the offspring from these experiments (i.e., the ‘grandchildren’) on 28 July and 9 August (DAR 108: 127, 129; see also DAR 108: 125). His overall results are given in ‘Illegitimate offspring of dimorphic and trimorphic plants’, pp. 410–18. In his conclusion (p. 436), CD asserted: ‘the illegitimate [i.e., homomorphic] offspring from an illegitimate union are hybrids formed within the limits of one and the same species’; consequently ‘the lessened fertility of the first union of the offspring of two forms is no sure criterion of specific distinctness’. CD also expounded these views in Origin 4th ed., p. 323, and in Variation 2: 184. For CD’s interest in cross and hybrid sterility, see Correspondence vol. 10, Appendix VI.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 28 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.

‘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.

Marginalia: Charles Darwin’s marginalia. Edited by Mario A. Di Gregorio with the assistance of Nicholas W. Gill. Vol. 1. New York and London: Garland Publishing. 1990.

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.

Origin 4th ed.: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 4th edition, with additions and corrections. By Charles Darwin. London: John Murray. 1866.

‘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.]

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

Vaucher, Jean Pierre Etienne. 1841. Histoire physiologique des plantes d’Europe ou exposition des phénomènes qu’elles présentent dans les diverses périodes de leur développement. 4 vols. Paris: Marc Aurel Frères.


Believes Lythrum is trimorphic. Asks AG for seeds of plants he suspects are polymorphic.

Letter details

Letter no.
Charles Robert Darwin
Asa Gray
Sent from
Source of text
Gray Herbarium of Harvard University (71)
Physical description
ALS 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 3685,” accessed on 27 May 2022,

Also published in The Correspondence of Charles Darwin, vol. 10