To G. H. K. Thwaites   20 June [1862]1

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

June 20th

My dear Mr Thwaites

By an odd chance, two days before receiving your letter of May 15th I wrote to you on Primula.—2

I am particularly glad to hear of Sethia. Menyanthes is said to be dimorphic like Primula; so I am not surprised at Limnanthemum;3 it will be a curious point to compare Villarsia (I have been blundering, I fancied Villarsia was diœcious.) with Menyanthes, if I can make out any difference in fertility in the two of Menyanthes.4 Have you any Malpighiaceæ? if so, I very much wish you would mark the imperfect flowers & see if they set seed.— Also whether they are closed, & whether the pollen-tubes are emitted from the pollen-grains within the anthers & then penetrate the stigma.— This is the case in the imperfect flowers of Viola & Oxalis.—5

Many thanks for your Governor’s letter: you do not say whether I am to return it, so I will keep it till I hear.—6

In Haste, pray believe me | yours very sincerely | Ch. Darwin—

I suppose it would be too troublesome for you to mark 12 a dozen plants of the two forms Limnanthemum & count the capsules, & compare the produce of seed by weighing or counting.— I suspect the dimorphism of Primula is often, (though not at all necessarily) the high-road to diœciousness.7

1
The year is established by the relationship to the letter from G. H. K. Thwaites, 15 May 1862.
3
In his letter of 15 May 1862, Thwaites reported that he had just read CD’s paper, ‘Dimorphic condition in Primula’, and that he had noticed the same phenomenon in the genera Sethia and Limnanthemum.
4
In Forms of flowers, p. 116, CD noted that the genera Menyanthes, Limnanthemum, and Villarsia constituted ‘a well-marked sub-tribe of the Gentianeæ’ and that all the species, as far as was then known, were ‘heterostyled’. CD had been anxious to see specimens of Menyanthes since he had learned earlier in the year that it was dimorphic (see letter to C. C. Babington, 20 January [1862], and letter from C. W. Crocker, 13 March 1862); he had recently acquired a short-styled specimen from the Royal Botanic Gardens, Kew (see letter to J. D. Hooker, 9 [April 1862] and n. 3). See also letter from G. H. K. Thwaites, 15 May 1862, CD annotations.
5
For CD’s interest in Viola and Oxalis, see also the letters to Daniel Oliver, 12 [April 1862] and 15 April [1862], the letter to J. D. Hooker, 30 May [1862], and the letter to Alphonse de Candolle, 17 June [1862].
6
See the enclosure to the letter from G. H. K. Thwaites, 15 May 1862. Charles Justin MacCarthy was the governor of Ceylon.
7
See ‘Dimorphic condition in Primula’, p. 95 (Collected papers 2: 61–2).

Manuscript Alterations and Comments

2.3 (I have been … diœcious.)] square brackets in MS
2.7 the pollen-grains] after del ‘wit’
5.2 forms] interl
5.3 Primula] before omitted point

Please cite as “DCP-LETT-3613,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-3613