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Darwin Correspondence Project

To J. S. Burdon Sanderson   15 August 1873

Bassett Southampton

Aug 15. 1873

My dear Dr Sanderson

I am much obliged for your letter which has been forwarded to me here—but I return home next Thursday—1 I assure you I felt quite guilty when I read in the Times your grand address on Physiology, at the thought that I had troubled you, at such a time, with my queries.2

I quite understand what you say about heat rigor.3

I shd think that it wd be extremely interesting to ascertain whether there is any electrical change in the leaves of Drosera when they are excited; but I shd think Dionæa wd be much better for the purpose. As far as I can imperfectly make out the lower surface of the leaf in Dionæa, & of the tentacles (i.e prolongations of the leaf) of Drosera is always in a state of tension, but is over mastered by the contraction of the upper surface alone—4

Therefore I imagine that the upper & lower surface wd exhibit an electrical change (if such there be) during the act of inflection   Now Dionæa, from the large size of the leaf & from the suddenness & greatness of the movement, wd be the best to operate on. If on further reflection you are willing to investigate this point, I wd gladly send you by a servant plants in good condition, for I suppose you wd require to have the plants at the Institute & not at Down—5

If you obtained any result, it seems to me that it wd be a remarkable discovery & well worth your publishing.—6

I had thought that it might be worth while to test Dionæa during inflection by the thermo-electric pile. A common thermometer gave no indication of any rise of temperature, so that it seems very doubtful whether the experiment wd be worth trying.7 If you find you have time & inclination to examine Dionæa or Drosera under the foregoing point of view, please to let me hear—

With many thanks yours very sincerely— | Charles Darwin


See letter from J. S. Burdon Sanderson, 13 August [1873]. CD stayed in Bassett, Southampton, from 9 to 21 August 1873 (see ‘Journal’ (Appendix II)).
Burdon Sanderson’s address on physiology, delivered to the Congress of the British Medical Association on 8 August 1873, was reported in detail in The Times, 9 August 1873, p. 10.
Drosera is the genus of sundews; Dionaea is a monospecific genus whose only species is Dionaea muscipula, the Venus fly trap. For Burdon Sanderson’s experiments on Dionaea, see the letter from J. S. Burdon Sanderson, 13 August [1873] and n. 7.
Burdon Sanderson was appointed the first superintendent of the Brown Animal Sanatory Institution in 1872 (G. Wilson 1979, p. 172).
Burdon Sanderson did not experiment with a thermopile (a device that converts thermal energy into electrical), but used a galvanometer (a device for detecting and measuring electric current) to record the nerve-like response of a leaf of Dionaea when stimulated with an induction coil (see Burdon Sanderson 1874, p. 128).


Wilson, Graham. 1979. The Brown Animal Sanatory Institution. Journal of Hygiene 83: 171–97.


Thinks it would be worth while testing for electrical changes in the leaves of insectivorous plants.

Please cite as

Darwin Correspondence Project, “Letter no. 9013,” accessed on 8 March 2021,

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