Dear Darwin

Strachey has been in the North, & has just written to say that he will gladly accept for Saturday 23^d.—¹

I have often speculated on the point you allude to, which is specially conspicuous in the Nelumbium.² Ferns & various Cryptogams do not show it as Phaenogams do.³ It is not conspicuous in other water plants as in Nelumbium which further holds its leaves high above the water, but for this association of the two means of getting out of the way as it were of injury from water, I should have supposed that both waxy coat & hairs were connected with absorption or respiratory functions.— I have lately wondered whether both may not subserve some purpose connected with Actinic or chemical rays of the Sun, especially as the waxy secretion is often more conspicuous on the upper leaf-surface—

The prevalence of indumentum on the under surface however points to transpiration in some cases; in others perhaps it is a provision against the attacks of insects, which harbor on under surfaces.

I can quite fancy water impeding both the actinic & calorific effects of sun-light on the leaf. We find watering most prejudicial in the hot sun. It is a splendid subject for experiments.⁴

Adam is a good man I believe, business-like & considerate— I hear that D. Galton is a thousand times worse than Ayrton & utterly detested in the office.⁵

The rehabilitating Ayrton with the Judge Advocacy, a sinecure suppressed by this very Ministry, is the jolliest job I have heard of for many a long day.—⁶

I will see to Oxalis at once⁷

Ever affec yours | Jos D Hooker