I suppose you know the slow way Drosera rotundifolia catches flies, doubtless for same purpose, though it can absorb the juices only through its bristles. I always thought it took in only the gases disengaged by putrefaction.
If you don’t know the trick of Drosera, which you should study, too, I will tell you, if you write to me at Sauquoit, Oneida County, New York.
Sauquoit, N. Y., July 17.
I have here yours of 13th.
If on leaf of Drosera rotundifolia, in good healthy condition, you put a small fly—somewhat crippled is surer—the sticky pellucid glands will hold him fast. By degrees (I have never seen it under ten or twelve hours at least) some of the bristles outside, which have not touched the fly, will turn inward and bring their sticky tip against the insect; later still others and more external ones turn in, and so the fly is bound by many liliputian bands. As it putrefies, I wonder if the leaf merely takes its chance of getting some of the disengaged gases, or whether it reabsorbs the clear fluid of the glands, charged now with some animal matter.
In transplanting some Drosera into a pan with wet moss, the older leaves may not work well; but the new ones developed soon will do better. Pray experiment upon this and Dionæa. I wonder if there ever were series of intermediate states between the inefficient Drosera, and the expert Dionæa....
August 21.
... I inclose half a letter which came from Darwin this morning. I hope you will go on with work on Dionæa....
C. DARWIN TO A. GRAY.
(Half of letter referred to above.)
Down, Bromley, Kent, August 8.
My dear Gray,—I have been glad to see Mr. Canby’s interesting letter on Dionæa, and I thank you for sending it; but unfortunately the facts are not new to me. Several years ago I observed the secretion of the “gastric juices” and the close adhesion of the two sides of the leaf when a fly was caught. I keep my notes in such an odd fashion that it would take me some time to find them. I am almost sure I ascertained the acid reaction of the secretion and its antiseptic power, but I cannot remember whether in this, or in analogous cases, I found its subsequent reabsorption. This letter fires me up to complete and publish on Drosera, Dionæa, etc., but when I shall get time I know not. I am working like a slave to complete my book.