# To Asa Gray   22 October 1872

Down, | Beckenham, Kent. [Sevenoaks, Kent.]

Oct 22d

My dear Gray

I have worked pretty hard for 4 or 5 weeks on Drosera & then broke down; so that we took a house near Sevenoaks for 3 weeks (where I now am) to get complete rest.—3 I have very little power of working now & must put off the rest of work on Drosera till next spring, as our plants are dying.4

It is an endless subject, & I must cut it short & for this reason shall not do much on Dionæa.— The point which has interested me most is tracing the nerves!!! which follow the vascular bundles. By a prick with a sharp lancet at a certain point, I can paralyse $\frac{1}{2}$ the leaf, so that a stimulus to the other half causes no movement.5 It is just like dividing the spinal marrow of a Frog:—no stimulus can be sent from the Brain or anterior part of spine to the hind legs; but if these latter are stimulated, they move by reflex actions.

I find my old results about the astonishing sensitiveness of the nervous system(!?) of Drosera to various stimulants fully confirmed & extended.—6

I want to beg you to make for me next spring two observations on D. filiformis, when growing vigorously & on a warm day.— I had the Kew specimens to experimentise upon; but am afraid of trusting to my results on 2 points.7

I write on next page the 2 experiments, (not difficult), & will you please keep the paper & try them for me next spring.—

Ever yours most sincerely | Ch. Darwin

My wife sends kindest remembrances to you both.—

Drosera Filiformis

(1) Put small atom of crushed fly on leaf near apex, & observe whether the solid leaf itself, after 24o or so, curls over the fly. This has nothing to do with the movement of the glands or hairs.

(2) Rub roughly with point of fine needle half a dozen times a few glands & observe whether they become inflected after a few minutes, or more probably after a few hours.

My results were negative on both these points, but I think it likely that they were so owing to want of vigour in the plant

Ch. Darwin

Oct. 22/72

## Footnotes

See letter from Asa Gray, 6 October 1872 and nn. 8 and 9. CD evidently received the pamphlet (A. Gray 1872b) later. CD refers to Jane Loring Gray.
In his letter of 6 October 1872, Gray had argued that the coiling motion in tendrils was always propagated downward and that coiling in tendrils that had not grasped anything started ‘under some inappreciable cause or stimulus’. In Climbing plants, pp. 95–8, CD explained how free tendrils turned round at the tip as many times as the number of spires (coils) formed, while caught tendrils curved spirally in opposite directions from both ends, in both cases to avoid self-twisting.
CD stayed at Miss Ann Woodington’s, the Common, Sevenoaks from 5 to 26 October 1872 (see ‘Journal’ (Appendix II) and letter to J. D. Hooker, 10 October [1872])).
Many temperate species of Drosera (sundew) die back in autumn.
Dionaea (Venus fly trap) is native to America. CD’s experiments in paralysing leaves were made on Drosera rotundifolia (see Insectivorous plants, pp. 247–50).
CD first researched Drosera from 1860 until 1862 and then intermittently while he was engaged in other research (see Correspondence vols. 8–10). He recommenced experimenting on Drosera in August 1872 (see ‘Journal’ (Appendix II)).
Drosera filiformis (the threadleaf sundew) is native to parts of the east coast of North America, including Massachusetts.

## Bibliography

Climbing plants: On the movements and habits of climbing plants. By Charles Darwin. London: Longman, Green, Longman, Roberts & Green; Williams & Norgate. 1865.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

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

## Summary

Spiralling of tendrils.

Has worked hard on Drosera.

Is interested in tracing the "nerves" of Dionaea which follow the vascular bundles. Finds he can paralyse half of the leaf by pricking it at a certain point.

Wishes AG to carry out two experiments on D. filiformis.

Has received AG’s Dubuque address [Am. J. Sci. 3d ser. 4 (1872): 282–98].

## Letter details

Letter no.
DCP-LETT-8568
From
Charles Robert Darwin
To
Asa Gray
Sent from