RECORD: Darwin, C. R. [1872-1873]. ['On the movement of the leaves of Drosera'], folio ?. CUL-DAR61.3-4. (John van Wyhe ed., 2002-. The Complete Work of Charles Darwin Online, http://darwin-online.org.uk/)
REVISION HISTORY: Transcribed and edited by John van Wyhe 2.2026. RN2
NOTE: See record in the Darwin Online manuscript catalogue, enter its Identifier here. Reproduced with permission of the Syndics of Cambridge University Library and William Huxley Darwin. The volumes CUL-DAR 54-61 contain material for Darwin's book Insectivorous plants (1875).
The volume CUL-DAR61 contains Darwin's draft essay 'On the movement of the leaves of Drosera', written 1872-1873. He intended to publish this with a revised edition of Climbing plants before commencing a larger book draft in April 1874 which became Insectivorous plants. See the introduction to this essay by John van Wyhe.
[3]
(a) These were chiefly Diptera; the largest kind which I saw caught was the small Heath Butterfly.
As some of the younger leaves could almost certainly lower [illeg] have succeeded in [illeg] subsequently seizing insects prey, that above proportion number fraction of 31/56 in 56 leaves does not probably give the full proportion. Many of the leaves had caught more than one insect; & on one very large leaf, I found remnants of at least a dozen thirteen insects. Considering th how extremely common this plant is on parts of Ashdown Forest & in many other places & in may other places the slaughter of insects must be prodigious.—
see below [3 words illeg]
(Over)
[See Insectivorous plants, p. 2.]
[3v]
No doubt insects destroyed on vast scale in apparently useless manner on by kinds of Horse-chestnut, as it is becomes almost of [illeg] apparent that with Drosera that are especial adaptation for catching insects. I concluded that the object was worth investigating — other observations
L[illeg] of poor soil
Roots
[4]
De[illeg] to leaf
A single prick with a needle in the middle of the leaf, or slight without touching any of the viscid hairs, or slightly rubbing the hairs, with a stiff camel-br pencil, caused [illeg]
Without any object , nothing being left on the leaf, causes the hairs & the edge of the leaf to curl inwards. Several stimulating fluids & A mere touch with needle or brush does not suffice sof
All solid objects, whether organic animal or vegetable or inorganic & as we shall see many certain fluids, when placed very gently on the leaf, so as to come produce as little irritations as possible, caused the hairs I edges of the leaf to close in. The body of an extremely small species of gnat, [illeg] with the wings or legs, torn off though so especially minute an object sufficed to cause the movement. The movement is necessarily slow; & generally takes from one to four or five hours; but it is impossible to measure the time accurately, as the age of the leaf, & the general state of the plant or of the temperature causes makes much difference in the required time.
The leaves close equally well in light & darkness.—
After a leaf has closed is on any object or from irritation, or over any object, it expands again; the time being dependent on the state of the leaf & on the nature of the object caught.
The same leaf will catch close & open flies at least twice probably many times successfully.) [remainder excised]
Citation: John van Wyhe, ed. 2002-. The Complete Work of Charles Darwin Online. (http://darwin-online.org.uk/)
File last updated 23 February, 2026