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Darwin Correspondence Project

To Edward Frankland   31 August 1874

Down, | Beckenham, Kent.

Aug 31 1874

My dear Professor Frankland

I hope that you will forgive me for once again troubling you.1 I am experimenting on Utricularia, which catches vast numbers of minute fresh water Crustaceans, which rot in the bladders. It cannot digest; but I find nitrate of Ammonia & urea act powerfully on it. Now what I want to know is whether towards the close of the putrefaction of flesh, skin &c, any substance is produced before the final resolution of the matter into gasses & salts of ammonia. I believe that Urea holds this position with respect to the living body; & it wd be very interesting to me to try any such substance (if such exists & can be procured) with Utricularia; As I am led to believe that the plant absorbs such products of decomposition.2

I wrote some time ago to you about the specific gravity of common phosphate of ammonia.3 As I did not hear in answer, I have used such information as I could get from Watts’ Dict., & I daresay this will be accurate enough for my purpose4

Pray believe | yours very sincerely | Ch. Darwin


Frankland had been helping CD with his work on insectivorous plants; see, most recently, the letter to Edward Frankland, 22 July 1874.
CD discussed Utricularia (bladderwort) in Insectivorous plants, pp. 395–453.
Frankland had not answered CD’s letter because he was travelling in Europe (see letter from Edward Frankland, 9 October 1874). CD’s annotated copy of Henry Watts’s Dictionary of chemistry (see Marginalia 1: 195–6) consists of the first three volumes of the second edition (Watts 1872–4), volumes four and five of an 1871 reprint of the first edition (Watts 1863–8), and a supplement to the first edition dated 1872 (Darwin Library–Down). In Insectivorous plants, p. 173 n., CD gave the specific gravity of phosphate of ammonia as 1.678, a figure given both by Frankland in his letter of 9 October 1874, and in Watts 1863–8, 4: 553.


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

Marginalia: Charles Darwin’s marginalia. Edited by Mario A. Di Gregorio with the assistance of Nicholas W. Gill. Vol. 1. New York and London: Garland Publishing. 1990.

Watts, Henry. 1863–8. A dictionary of chemistry and the allied branches of other sciences. 5 vols. London: Longman, Green, & Co.

Watts, Henry. 1872–4. A dictionary of chemistry and the allied branches of other sciences. 2d edition. 5 vols. London: Longman, Green, & Co.


Utricularia catch freshwater Crustaceans, which cannot be digested and rot in the bladders. CD is interested to identify any substance produced in the putrefaction before it is resolved into gases and salts of ammonia. He has reason to believe that the plant absorbs such products.

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. 9614A,” accessed on 24 September 2021,

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