To G. H. K. Thwaites   15 June [1862]1

Down. | Bromley. | Kent. S.E.

June 15th

My dear Mr Thwaites

If you see Linn. Journal, I hope that you will read my paper on the fertilisation of Primula.2 Why I hope that you will do this, is because I have been told that Dr. Weddell states that Cinchona presents the same case of some individual trees with long pistils & some with short.3 Now if this be the case, it is almost certain that in order to get good seed & good seedlings there must be reciprocal fertilisation between the two forms. It is quite likely, but by no means certain, that Ceylon insects may do this work effectually; but the subject, I am sure, is worth your attention.

If there be any difficulty in getting seed in Ceylon, or in raising strong plants from Ceylon seed, do I beg you, try artificial fertilisation on a few dozen flowers, making the cross between the two forms.— There is no need of castration   The growth of Cinchona is so important for mankind, that I am sure you will excuse my making this suggestion.4 It is a subject I am still working at.5 This form of dimorphism seems common with the Rubiaceæ;6 & if you have observed any analogous facts I shd. be grateful for information.—

I sincerely hope that you are well & in all ways prosperous.—

Pray believe me | Yours very sincerely | Ch. Darwin

1
The year is established by the relationship to the letter to G. H. K. Thwaites, 20 June [1862].
2
CD read his paper, ‘Dimorphic condition in Primula’, before the Linnean Society of London on 21 November 1861 (see Correspondence vol. 9); the paper was published in the number of the society’s Journal issued on 1 March 1862 (General index to the Journal of the Linnean Society).
3
A ‘rather tall man with upturned eyebrows’ gave CD this information, after hearing CD’s paper on Primula, at the Linnean Society meeting on 21 November 1861 (see Correspondence vol. 9, letter to J. D. Hooker, 25 November [1861]). The reference is to Hugh Algernon Weddell, a specialist on the flora of South America who had made a detailed study of Cinchona (see, for example, Weddell 1849).
4
Cinchona trees were valued on account of their bark, the source of quinine, an effective febrifuge or antipyretic medicine. The enormous demand for the bark and the wasteful manner in which it was procured from South America led to fears that supplies would soon be exhausted. From the middle of the nineteenth century, attempts were made to introduce the most valuable Cinchona species into Asian localities likely to support their cultivation; in the 1850s, the Dutch introduced the trees to Java, and, in the 1860s the British established plantations in India and Ceylon (EB).
5
CD was investigating the possible occurrence of dimorphism in a number of species, particularly in several members of the Melastomataceae (see, for example, letter to Asa Gray, 10–20 June [1862]).
6
Cinchona is a member of the Rubiaceae. Asa Gray told CD of the dimorphic nature of many Rubiaceae in his letter of [27 and 29 August] and 2 September 1861 (Correspondence vol. 9), and mentioned Houstonia as a good example on which to experiment (see ibid., letter from Asa Gray, 11 October 1861). Gray had recently examined plants of this genus for CD (see letter from Asa Gray, [2 June 1862]). See also Correspondence vol. 9, letter from George Bentham, 26 November 1861.

Manuscript Alterations and Comments

1.2 Dr] added
2.2 Ceylon] above del ‘the’
2.2 , making] over ‘.—’
2.3 There is no need of castration] interl

Please cite as “DCP-LETT-3606,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-3606