My dear Sir

D^r. 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 sh^d 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