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

LS

4
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.
5
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.

Please cite as “DCP-LETT-9481,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-9481