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Darwin Correspondence Project

To Edward Frankland   7 October [1873]1

Down, | Beckenham, Kent.

Oct 7th

My dear Sir

Whenever you write about the acid secreted by Drosera, will you have the great kindness to give me a piece of the most sensitive Litmus paper which can be prepared.—2 I have some bought from a druggist, but know not whether it is very sensitive.—3 I am examining certain hairs on plants, which secrete minute drops of viscid matter & thus catch minute flies, & I want to know whether this is ever acid.—4

My dear Sir | Yours sincerely | Ch. Darwin


The year is established by the relationship between this letter and the letter to Edward Frankland, 29 September 1873.
CD had asked Frankland to analyse the secretions of the insectivorous plant Drosera (sundew; see letter to Edward Frankland, 29 September 1873).
CD usually ordered litmus paper from his chemist, William Walmisley Baxter (see letter to W. W. Baxter, 11 May [1860–2 or 1872–4?], Calendar no. 8319, to be published in a future supplement).
CD discussed the power of absorption of the glandular hairs of plants other than the insectivorous Drosera and Drosophyllum lusitanicum (Portuguese sundew or dewy pine) in Insectivorous plants, pp. 344–55. He mentioned the acidity of the secretion of only one of them, Primula sinensis (the secretion was not acid; ibid., p. 348).


Calendar: A calendar of the correspondence of Charles Darwin, 1821–1882. With supplement. 2d edition. Edited by Frederick Burkhardt et al. Cambridge: Cambridge University Press. 1994.

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


Requests a piece of the most sensitive litmus paper in order to test the secretions of minute hairs of plants which catch minute flies. [See 9098.]

Letter details

Letter no.
Charles Robert Darwin
Edward Frankland
Sent from
Source of text
The John Rylands Library, The University of Manchester
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 9090A,” accessed on 27 October 2021,

Also published in The Correspondence of Charles Darwin, vol. 21