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Darwin Correspondence Project

To W. T. Thiselton-Dyer   4 June 1874

Down, | Beckenham, Kent.

June 4 1874

My dear Professor Dyer

I am greatly obliged to you about the Opuntia, & shall be glad if you can remember Catalpa.1 I wish some facts on the action of water, because I have been so surprized at a stream not acting on Dionæa & Drosera. Water does not act on the stamens of Berberis; but it does on the stigma of Mimulus. It causes the flowers of the bedding-out Mesembrianthemum & Drosera, to close, but it has not this effect on Gazania & the daisy; so I can make out no rule.2

I hope you are going on with Nepenthes;3 & if so, you will perhaps like to hear that I have just found out that Pinguicola can digest albumen, gelatine &c.4

If a bit of glass or wood is placed on a leaf, the secretion is not increased, but if an insect or animal matter is thus placed, the secretion is greatly increased & becomes feebly acid, which was not the case before. I have been astonished & much disturbed by finding that cabbage seeds excite a copious secretion, & am now endeavouring to discover what this means.5 Probably in a few day’s time I shall have to beg a little information from you, so I will write no more now.

With many thanks, | yours very sincerely | Ch. Darwin

P.S. I heard from Asa Gray a week ago, & he tells tells me a beautiful fact; not only does the lid of Saracenia secrete a sweet fluid, but there is a line or trail of sweet exudation down to the ground so as to tempt insects up.6


CD’s notes on the experiments he carried out on digestion in various species of Pinguicula (butterwort) in June and July 1874 are in DAR 59.1 33–119; his notes for 1 June 1874 are in DAR 59.1: 35. See also Insectivorous plants, pp. 382–3.
CD concluded that Pinguicula was able to derive nutrition from nitrogenous vegetable matter as well as from animal matter; see Insectivorous plants, pp. 374, 385–90. CD’s notes on experiments with cabbage seeds carried out between 5 June and 25 July 1874 are in DAR 59.1: 47 and 93.


Insectivorous plants. By Charles Darwin. London: John Murray. 1875.


Discusses effects of water on movement of insectivorous plants.

Has just found that Pinguicula can digest albumen.

Asa Gray writes that Sarracenia secretes trail of fluid to attract insects [see 9455].

Letter details

Letter no.
Charles Robert Darwin
William Turner Thiselton-Dyer
Sent from
Source of text
Royal Botanic Gardens, Kew (Thiselton-Dyer, W. T., Letters from Charles Darwin 1873–81: 8–9)
Physical description
LS 3pp

Please cite as

Darwin Correspondence Project, “Letter no. 9481,” accessed on 10 June 2023,

Also published in The Correspondence of Charles Darwin, vol. 22