To W. T. Thiselton-Dyer   19 [May 1878]1

Down, | Beckenham, Kent. | Railway Station | Orpington. S.E.R.

April 19th

My dear Dyer

I am heartily obliged for the plants & seeds which arrived safely & several of them will be of extreme use to me.—2

I hope that you will give from me my thanks to Mr. Lynch.—3

With respect to the tiny plants of Melocactus they are much too old; what I require to see is the plumule or cotyledons (as the case may be) as or before they break through the ground.4 I have therefore been thinking that it wd be the best plan for us to attempt again raising seeds of some Cacteæ, for I forgot that the pots require for my purpose to be daily examined. Will you therefore ask Mr Lynch to let me have any seed or fruit, which he can get of any Cacteæ (avoiding Opuntia nigricans & Rhipsalis cassytha, which so disgracefully failed with us);5 asking him moreover to mark on packet what temperature & kind of soil they ought to be sown in.—

From same cause it wd be better to send me a few seeds of Pachira with instructions about sowing.6 This in the long run wd. give less trouble than raising seedlings for me.—

I was very much interested with your last letter about protoplasm, &c, about which I have sometimes thought though knowing very little.7 As the cell-walls grow I do not see why light, gravity contact &c—shd. not act on them directly, instead of through the protoplasm.— When examining Drosera, I took the impression that the cell-walls were undervalued.8

It is a frightfully difficult subject, & I shall avoid it, keeping to facts as much as possible.—

We are very sorry to hear not a very good account of Mrs. Dyer: some time ago we heard a very prosperous account.—9

Yours very sincerely | Ch. Darwin

1
The month and year are established by the relationship between this letter, the letter to W. T. Thiselton-Dyer, 9 May [1878], and the letter from W. T. Thiselton-Dyer, 11 May 1878. CD evidently wrote 19 April by mistake.
2
CD had requested seeds and plants from Kew in his letter to W. T. Thiselton-Dyer, 9 May [1878].
3
Richard Irwin Lynch was the foreman of the propagation department at the Royal Botanic Gardens, Kew.
4
CD was studying the development and movements of the first shoots and leaves of the plant embryo; he later observed that in many Cacteae (a synonym of Cactaceae) the cotyledons were rudimentary but probably served to protect the plumule when it broke through the soil in an arch (Movement in plants, pp. 96–7). Melocactus is the genus of melon cacti, found from Mexico to central South America.
5
Opuntia nigricans (a synonym of Opuntia elatior, prickly pear) is a cactus native to South America. Rhipsalis cassytha (a synonym of Rhipsalis parasitica subsp. parasitica, mistletoe cactus), is found in Africa and Sri Lanka as well as in the Americas. According to a list of plants sent from Kew on 25 March 1878, CD had received a plant of Rhipsalis cassytha (DAR 209.12: 185).
6
CD had asked for seeds of Pachira aquatica (Guiana chestnut or provision tree). See letter to W. T. Thiselton-Dyer, 14 May 1878 and n. 5.
8
Sydney Howard Vines had explained the loss of extensibility in the cell wall as a secondary effect of the paralysis of the protoplasm, which was caused by light (letter from W. T. Thiselton-Dyer, 11 May 1878 and n. 3). CD had studied the inflection of the tentacles in leaves of Drosera rotundifolia (common or round-leaved sundew); he presented conflicting views on the physiological processes involved, noting that both elasticity of the cell wall and contraction of the protoplasm had been suggested as explanations for the inflection (Insectivorous plants, pp. 256–9).
9
In his letter of 11 May 1878, Thiselton-Dyer mentioned going away to the seaside with his wife, Harriet Anne Thiselton-Dyer. Harriet had given birth to her first child on 9 April 1878 (Allan 1967 s.v. ‘Hooker pedigree’).

Manuscript Alterations and Comments

1.1 & seeds] interl
1.1 several] above del ‘some’
3.7 moreover] above del ‘moreover’
4.1 it] after del ‘I’
4.2 run] above del ‘run’

Please cite as “DCP-LETT-11479,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-11479