My dear Sir

I was pleased to see your handwriting again, & sincerely hope that you are quite recovered from your long illness. Take warning from me & do not work too hard.— Very many thanks for information about P. ciliata & var.—² I was sure it could not be an ordinary variety; it differed too much & I was utterly perplexed what to do about it.—³ I sh^d. have much liked to have seen P. farinosa, but I well knew that you could not send it, else you would have done so.—⁴

I hate changing work & I have so many irons in the fire that I have stopped looking after Dionæa.— I return your nice sketches which make me quite envious. I do not of course mean to attempt any minute work at structure; merely a few functional observations relatively to Drosera (which alas I have resolved to put off for another year, for I have amused myself too long over Primulas & Orchids).—⁵

I have made out very little on Dionæa: merely that the leaf behaves very differently when a fly, or only bit of cork & nothing is caught.— When a fly is caught much acid mucous is poured out as in Drosera. And the leaf must absorb so as to perceive when it has caught a fly— The “tortoises” seem to be the secretors & absorbers & appear to me to be strictly homologous with the glands in Drosera.— It is odd that meat, flies, sol. of C. of ammonia, will not excite movement or secretion; the sensitive filament must be touched to set all in action. The sensitiveness of the filament is prettily adapted: drop of water falling on them, or strong wind through pipe produces no effect; but a touch by a woman’s Hair held with one inch length free will suffice. There is a pretty difference with Drosera: the latter does not care for a single rough touch with even a needle, but a weight left on the gland of $\frac{1}{\mathrm{70,000}}$of a grain will excite movement; & this is good for plant, for it has to clasp an insect when resting on & sticking to the gland: it would be lost labour to Drosera to close when merely touched by large insect.— In Dionæa, a far lighter single touch by mere hair causes movement; but a much greater weight, if put on delicately, may be left on the filament, without exciting movement than with Drosera.—

But I must not run on. | Pray believe me | Yours very sincerely | Charles Darwin