My dearest F.

Before answering your long letter, there are a few miscellaneous points to touch on.—² You audacious dog I have answered about Printing machine without the aid of red-pencil &c.— I rather hope you will feel inclined to give it to Semper.³

I have got branch of Porliera with Quick-lime, & fancy it has produced very slight effect. Your rain-case with Porliera is capital: when leaflets are asleep about $\frac{2}{3}$ of under surface is protected or covered by next leaflet behind, & I imagined that perhaps there w^d be very few or no stomata in the unprotected part.—⁴

In the proceeding of K. Akad. d. Wissenschaften in Wien. In No XVI just received there is long abstract of great Paper or book by Wiesner on Heliotropism & Geotropism: it seems very important, but I cannot understand it; do get it at Wurzburg & read it; my puzzle is at p. 139, what on earth he means by “Induction”.— Perhaps Sachs will have read it— After you have read it; if you do not understand talk to him about “Induction”.—⁵

I have nearly finished with Thalia— it is a wonderful case, but not worth the time which I have spent on it; as I now find through Dyer that Delpino has described an allied genus, but seems to have entirely missed the interesting point of sensitiveness.—⁶

I partially agree with what Sachs says about the distinction between the circumnutation of free twiners, & the subsequent growth on one side after they have twined round a support; that the growth then is almost exclusively on one side alone is, I think, shown by their clasping the stems very closely; but they slide a little up the support in their coiled state which seems to show that there must be a little growth on all sides.— Nor can I see why the part beyond point of contact sh^d at once stop circumnutating. This seems well worth investigating.— There is nothing about this, I believe, in my book, except the fact of sliding up, & I had not thought of it in relation to our general view of modified circumnutation.— At p. 131 of 2^d Edit there is the passage about circumnutation of tendrils stopping when apogeotropism comes into action; but you must remember that I there speak only of conspicuous circumnutation.⁷ Lately I have observed several plants; laid on one side for apogeotropism to act carefully by tracing, & the line is sometimes quite straight, but more commonly slightly zig-zag, showing a vestige of circumnutation, just as with Heliotropism.

At—p. 129 of Climbing book there is fine case of modified circumnutation in order for tendril to pass over terminal shoot.⁸

I never tried turning a twined plant upside down; so your fact new to me.—⁹

I told De Vries the case about tips of tendrils (p. 132) was well worth investigating in relation to growth, & he seemed to agree.—¹⁰

The contraction of tendril into spire, which is so important for the plant, seems another case of modified circumnutation or rather, I suppose, of growth prolonged on one side alone after it has ceased on all other sides.— I cannot believe that a tendril curling when touched in less than 1m. is due to growth; & De Vries seemed in a letter to me staggered by my arguments.¹¹

You must remember when I wrote the 1^st Edit. of Climbers, I knew very little about growth or cause of circumnutation. I do not know whether I have answered what you want to know, & whether this note will be intelligible. You have given me fine list of Sleepers.¹²

It is very odd about wet & dry culms of grass & sticks: does Sachs understand it.—¹³

Something made me think the other day that aggregation in roots from C. of Ammonia, w^d be in your line & w^d. be fine subject: a little wild Euphorbia showed it plainest, & a wonderful phenomenon it was.—¹⁴ I wonder no one has taken it up.

Bernard gets more & more charming: he rebuked me sternly yesterday, because I said he was going in a booboo, whereas I ought to have said a gee-gee.—¹⁵

Dearest old Backy | C. D.—

I fear this letter will bother you to read.