Dear Sir

As one of my sons is going to Cambridge tomorrow, I have thought it worth while to send a plant of Dionæa, (which c^d. not be packed safely for Railway carriage) to you for the chance of your being still willing to investigate any change of temperature in it when in action.—² The pot had better stand in $\frac{1}{4}$ of an inch of water in saucer—: it ought to be in the light & in warm room. There are only 2 leaves fit for action (marked with red wool), & these will probably be closed by the jars incident on travelling. When a leaf closes on no object it does not generally open for 12^o to 24^o. If it closes over a large fly or meat it remains shut for several days, & is never active again. I doubt whether a cut-off leaf standing in water will reopen; but I have never tried this. It might close from the act of cutting off. The two active leaves have terribly short foot-stalks. It is scarcely possible at this season to procure better plants.

If possible, I w^d strongly recommend the following trial, viz to compare the temp. of 2 leaves whilst still on the plant, & I suppose they w^d. necessarily be almost the same, & then to make one close by dropping or placing on the surface a bit of roast meat, or a large crushed fly, & observe whether the temp. changes.— But the point which seems to me the most interesting w^d be to observe after about 18^o to 24^o, when the closed surfaces of the leaf are still actively pressed together, & are copiously secreting & at the same time absorbing, whether the temp. does not rise. So much vital action ought,, I sh^d. think, to produce this result.³ I wish with all my heart the plant was a better one; but I have given away all my best specimens for B. Sanderson’s electrical experiments, which have proved so wonderful.—⁴

Dear Sir, Yours faithfully   Ch. Darwin