My dear Father,

Sachs doesn’t know of any negative heliotropic mould; in the Texbook (English) p 677 he says marchantia root hairs & roots of Brassica & Sinapis are negatively heliotropic²   Sachs came in much delighted the day before yesterday having found a number of shoots of Menispermum which had contracted into beautiful corkscrews without having had any sticks given them just as if they were tendrils— he seems to me to jump to conclusions rather; he seems to think now it will be perfectly easy to make out a good case for the similarity of tendrils & twiners. He also found Akebia which had grown down a stick twining round it.³ I have made out clearly that the number of windings increase in the part of the stem that is already wound round the support; that is to say it is not merely the growth of the free end of the shoot, but the growth of the part already touching the support that comes into play. I expect I shall have to come back here to work it out next summer. Sachs promises me a whole greenhouse full of all the plants I want if I can come, but shall certainly go on with it at Down. It is Sachs idea so that if it is to be any good it ought to be done here.

Sachs observed last night a plant of Anagallis pratensis which sends out leafy stems over the ground like Lysimachia, & he said that it was so at night with the bud at the end bent right over.⁴ I have found a malvaceous plant which sleeps.⁵

The stalk does not alter but the leaf is 50^o below Horizon at night & 10^o above in the day; the leaf stalk is a little thickened close to the leaf   Gossypium has a gland on midrib underneath which secretes & is much visited by ants here in the houses.⁶

I hope you are not bang dead with work dear father | Your affec son | Frank Darwin

See also p. 757 note on Rhizomorphs or root like mycelium of true funguses   There is more about it in 4^th Edit   There seems a doubt whether they are apheliotropic after all⁷