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Darwin Correspondence Project

To Lawson Tait   13 June [1875]1

Abinger Hall | Wotton Surrey

June 13th

My dear Sir

All the part in my Book on the Droseraceæ is printed off, so it wd. be of no use sending me the details of your observations.—2 Judging from mine the ferment is not present in the secretion of D. rotundifolia until the glands have been excited by absorbing a peptogene (Schiff).3 But I believe the ferment is ready secreted by Drosophyllum;4 & as D. binata (= dichotoma) is more nearly allied to Drosophyllum than any other sp. of Drosera, the ferment may be ready secreted in this species.—

I was aware that the secretion of D. rotundifolia curdles milk, like rennet & like the secretion of Pinguicula, but my observations were not detailed enough to do more than just allude to subject.—5

Yours sincerely | Ch. Darwin


The year is established by the relationship between this letter and the first letter from Lawson Tait, 12 June [1875].
In his first letter of 12 June [1875], Tait had discussed his isolation of a pepsin-like compound from fluid produced by leaves of Drosera dichotoma (a synonym of D. binata, the forked-leaf sundew). Most of CD’s experimental work was on Drosera rotundifolia, the subject of the first eleven chapters of Insectivorous plants.
In Insectivorous plants, p. 129, CD cited Moritz Schiff’s work on the physiology of digestion (Schiff 1867) for the information that in animals pepsin was secreted only in the presence of soluble substances that Schiff had called peptogenes.
Drosophyllum (dewy pine or Portuguese sundew) is a monospecific genus of insectivorous plants that was formerly placed in the family Droseraceae, but is now in the family Drosophyllaceae.
See first letter from Lawson Tait, 12 June [1875] and n. 4. In Insectivorous plants, p. 384, CD mentioned that drops of milk placed on a leaf of Pinguicula (butterwort) curdled after a few hours, but he did not expand on the observation. For more on CD’s interest in the use of Pinguicula as a curdling agent, see Correspondence vol. 22, letter to W. T. Thiselton-Dyer, 26 June 1874 and n. 7.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

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

Schiff, Moritz. 1867. Leçons sur la physiologie de la digestion, faites au Muséum d’histoire naturelle de Florence. 2 vols. Florence: Hermann Loescher.


RLT’s observations come too late, as CD’s book on Droseraceae has been printed.

Reports on his observations of ferment in secretions in Drosera rotundifolia and Drosophyllum.

Letter details

Letter no.
Charles Robert Darwin
Robert Lawson (Lawson) Tait
Sent from
Abinger Hall
Source of text
DAR 221.5: 26
Physical description
2pp (Photocopy)

Please cite as

Darwin Correspondence Project, “Letter no. 10017,” accessed on 27 February 2021,

Also published in The Correspondence of Charles Darwin, vol. 23