My dear Gray

It was very good of you to write me your long letter of Oct. 6^th, telling me of your & M^rs Gray’s wonderful doings, about which I was very glad to hear.— Alas I never received your Dubuque address, but I have seen a short extract from it on Sequoia.—¹ One word more about Tendrils: I would gladly accept your view to account for the spiral winding of a tendril, which has clasped nothing, had it not been for the fact of the same tendril, when it has clasped an object, contracting in opposite directions, in equally close spiral curvatures.— The concave side of the lower part, in this latter case, can hardly have contracted. I think I have explained the proximate cause of the reversed spiral curvature, but I cannot understand the more remote cause.²

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 24^o 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