# To Daniel Oliver   11 September [1860]1

Down Bromley Kent

Sept 11th

My dear Sir

Dr. Hooker told me that you would be so kind as to observe rate of closing of leaf of some Australian Drosera,2 if it does close its leaf over flies.

There are two other points, on which I shd be infinitely obliged for a little information. Lindley speaks on the closing of the leaf of Drosera lunata of India, in a manner which makes me suppose that it closes in a more marked manner that our Drosera;3 I see Steudel in his Nomenclator refers to Buchanan & Wight,4 would it give you much trouble to refer to these Authors & see whether they say anything on the subject.—

Lastly would you look at the Dionæa (if you have living specimen) & observe whether the hairs are viscid, for it almost passes my belief that the leaf can snap so quick as to catch a fly, unless it be in some degree entangled: when a fly is caught it is said to be bathed with a secretion, as in case of our Drosera.—5

Pray forgive me troubling you so much & believe me | My dear Sir | Yours very faithfully | C. Darwin

P.S. I believe one of your Gardeners artificially stirred up pollen in the indusium of Leschenaultia formosa at my request.6 Will you ask whether it has made Pods. My plant has made pods on those flowers, which I thus treated. Whether my seeds will ripen I doubt, but I can see seeds through walls of pod.—

P.S. | I have written to Gardeners Chron. to ask for authority of movement of leaves of D. lunata.—7

You will think it incredible but it is a fact that genererally $\frac{1}{1920}$ th part of single grain of Nitrate of Ammonia (nitrogen in both base & acid) causes decided movement of leaf. Even $\frac{1}{2400}$ th of a single grain sometimes causes movement, & I am myself convinced (though I do not expect any one to believe without ocular evidence) that $\frac{1}{2880}$ th of a grain occasionally produces an effect on very sensitive & young leaves.—   Are not these facts curious, ie if you can swallow them. Believe me that they are not stated without numerous & carefully repeated experiments.—8

## Footnotes

Dated by the relationship to the letters to J. D. Hooker, 2 September [1860] and 6 September [1860].
See letter to J. D. Hooker, 2 September [1860].
Lindley 1846, pp. 433–4. See letter to Gardeners’ Chronicle, 15 [September 1860].
Francis Hamilton Buchanan and Robert Wight were cited in Steudel 1841, p. 531, as the first to identify Drosera lunata. CD’s copy of Steudel 1841 is in the Darwin Library–CUL. Buchanan and Wight were specialists in the flora of India. The point about which CD was inquiring is not discussed in Insectivorous plants.
The Venus’s fly-trap (Dionaea muscipula) is described in Insectivorous plants, pp. 286–320. CD states that the surface of the leaf of this plant is thickly covered with minute glands (ibid, p. 287). In addition, the leaves have several rows of sensitive filaments that ‘are not viscid, and the capture of insects can be assured only by their sensitiveness to a momentary touch, followed by the rapid closure of the lobes.’ (ibid., p. 290).
See letter to J. D. Hooker, 11 May [1860].
See letter to Gardeners’ Chronicle, 15 [September 1860] and n. 3.
CD’s notes on experiments carried out in July, August, and September 1860, in which he tested the effects of various substances on the leaves of Drosera, are in DAR 60.1.

## Summary

Requests observations on Drosera and Dionaea,

and asks DO to look up Buchanan and Wight on insectivorous plants ["Conspectus of Indian Utricularia", Hooker’s J. Bot. 1 (1849): 372–4].

## Letter details

Letter no.
DCP-LETT-2913
From
Darwin, C. R.
To
Oliver, Daniel
Sent from
Down
Source of text
Down House (MS 10: 9)
Physical description
6pp