My dear F.

Many thanks for all you have done for me.— Keep notes— Why I wish to know about sleeping plants is to give list of Families, as I have observed a good many new cases.—² My Porliera has had no water for some time, but shows no sign of flagging.³ I have been intending for some time & hope tomorrow to enclose a twig, still on the tree, in bottle with quick-lime, to see effects of locally very dry air.

I have been working very hard all the week, chiefly at Thalia, & at last I have made out whole mechanism: it is a wonderful case— the excitement from a touch spreads from 2 filaments over nectar (which filaments are prolongations of a petal or strictly a staminoid) to the pistil, which instantly (certainly as quickly as Dionæa) curls up into a spire, sweeps the bristle to the opposite side of flower, covering it with pollen, & holding it in a special fold or notch. Just as with Catasetum I c^d never help jumping when the pollinia were ejected, so here the sudden snap with which the pistil coils up always makes me jump.⁴

I have now observed the movements of a score of leaves & of many sleepers, so as to compare the nature of their movements, & it is clear to me that sleep is merely modified circumnutation at a particular time of the day.—

You know some leading shoots are always hooked & I have been observing how they straighten themselves: this again is circumnutation with an excess of movement on the under side of the bowed or convex part. Does not Pfeffer call this hynasty & epinasty or some such names? If you can, do talk about this movement of Pfeffer with Sachs;— it does not seem to me to deserve a special name.—⁵

Lastly I have a good case with Acacia retinoides of leaves from which bloom had been removed in February being attacked with black smut.⁶

I hope that you get on with German & profit in many ways from what you see in the Institut.—

How nice it will be to have you home again. Bernard is very sweet & pretty.⁷

Ever yours affect | C. Darwin

I send Nature⁸

P.S. Horace suggests that you ask permission to water copiously the plant of Porliera which is out of doors & see if it will then keep awake all day.—⁹

P.S. | Very many thanks about Sleepers just received— The great thing is fresh Families. I have a Malvaceous plant, but not genus Gossypium so this w^d be valuable fact if it sleeps— Do not waste time abt more Leguminosæ unless you see something remarkable & new—¹⁰

I do not see that any one (except you occasionally) uses the machine. It is an ugly object in the Smoking Room & I sh^d. think it a very good thing for me to send it as a present to Sachs   You decide.— I am sure that I shall never endure to have my M.S. copied— Horace does not object to its being given.— All this is written under a mistake— I thought it was Sachs & I see it is Semper— Nevertheless I sh^d not at all object to give it to Semper— If you decide so, (I do not care an atom about it) it ought to be cleaned & despatched & packed by makers¹¹