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Darwin Correspondence Project

From Lawson Tait   12 June [1875]1 

7, Great Charles St. | Birmingham.

June 12

My Dear Sir,

Another point that may interest you.

The glands of Drosera dichotoma (australian) are constantly covered with the viscid secretion, its action being exactly that of the D. rotundifolia.2 

I gathered a lot of the fluid and by Brücke’s method I have been able to separate a nitrogenous matter with a very close resemblance to pepsine.3 

It is not pepsine, but I propose meantime to call it droserin. If you would like the details of my experiments & the process I shall be glad to send them. It has a curious action on milk, amongst other things, resembling but not identical with rennet. I suppose you know that old Gerrards says that D. rot. was very much used in Cheshire in his days for rennet.4 

I have just had a summons & am just off to Shrewsbury

Yours, faithfully, | Lawson Tait

Please don’t trouble to write an answer to this more than a post card to say if you would like the particulars.


The year is established by the relationship between this letter and the letter to Lawson Tait, 4 June [1875].
Drosera dichotoma is a synonym of D. binata (the forked-leaf sundew); D. rotundifolia is the common or round-leaved sundew. Tait refers to the digestive action of the secretion of the leaf-glands.
Ernst Wilhelm von Brücke described his method for isolating the digestive agent pepsin in his paper ‘Beiträge zur Lehre von der Verdauung’ (Contributions to the theory of digestion; Brücke 1861, pp. 618–19).
John Gerard described two species of sundew, Ros Solis major and Ros Solis minor (Drosera rotundifolia and D. intermedia, the spoonleaf sundew) in his herbal (Gerard 1597, pp. 1366–7). He did not mention its use as a rennet substitute in this description. He did, however, mention that Cheshire cheese was made with a rennet substitute made from the flowers of yellow or lady’s bedstraw (Galium verum; Gerard 1597, p. 1128) or from English saxifrage (now called pepper-saxifrage, Silaum silaus; Gerard 1597, p. 1048).


Brücke, Ernst Wilhelm. 1861. Beiträge zur Lehre von der Verdauung. Sitzungsberichte der Akademie der Wissenschaften in Wien. Mathematisch-naturwissenschaftliche Klasse 43 (2d part): 601–23.

Gerard, John. 1597. The Herball, or, Generall historie of plantes. London: John Norton.


Has separated out a pepsin-like substance from the secretion of Drosera, which he proposes to call "Droserin".

Letter details

Letter no.
Robert Lawson (Lawson) Tait
Charles Robert Darwin
Sent from
Source of text
DAR 178: 9
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 10015,” accessed on 14 April 2021,

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