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Darwin Correspondence Project

From W. T. Thiselton-Dyer   5 June 1874

10 Gloucester Road | Kew

June 5. 1874

Dear Mr Darwin

Let me thank you very much indeed for your most interesting letter.1 I venture to make one suggestion in respect to the Pinguicula which I fancy at the same time can hardly have escaped you

The seeds of the species of Brassica are very rich in Nitrogen. A familiar illustration of this is the fact that Rape cake (Brassica campestris)2 which is the residue after the expression of the oil is employed as a food for cattle and when damaged is even used as a nitrogenous manure. I find on referring to Knop’s tables that Rape seed contains (air dried) nearly 20 per cent of albuminoids3

Believe me | Yours very truly | W. T. Thiselton-Dyer


Brassica campestris (rape) is a synonym of Brassica rapa. Although CD had started experiments using cabbage seeds (Brassica oleracea) on 3 June 1874 (DAR 59.1: 39), and had reported that to Thiselton-Dyer (letter to W. T. Thiselton-Dyer, 4 June 1874), there is no record that he used rapeseed in his experiments with Pinguicula (butterwort).
According to Wilhelm Knop’s handbook of agricultural chemistry, rapeseed contained 19.4 per cent ‘Eiweisskörper’ (albuminoids) (Knop 1868, 1: 719; see also 1: 695).


Knop, Wilhelm. 1868. Der Kreislauf des Stoffs. Lehrbuch der Agricultur-Chemie. 2 vols. Leipzig: H. Haessel.


Sends information on nitrogen and albuminoid content of seeds of Brassica.

Letter details

Letter no.
William Turner Thiselton-Dyer
Charles Robert Darwin
Sent from
Source of text
DAR 58.1: 56–7
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 9484,” accessed on 27 January 2021,

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