To J. D. Hooker   13 August 1873

My dear Hooker

We return home on Thursday the 21^st & I hope it will suit you & Gen. Strachey to come down to us on Sat.¹ Let us hear beforehand. When you come to Down I want a little information from you, & if you do not yourself know, please to enquire of some of the wise men of Kew. Why are the leaves & fruit of so many plants protected by a thin layer of waxy matter (like the common cabbage) or with fine hair; so that when such leaves or fruit are immersed in water they appear as if encased in thin glass. It is really a pretty sight to put a pod of a common pea, or a raspberry into water   I find several leaves are thus protected on the under surface & not on the upper.

How can water injure the leaves? if indeed this is at all the case.²

When you were abroad I wrote to Mr Smith to ask for a plant of oxalis sensitiva; & he sent me one, but the leaves are so old that they will not act well. Could you give me a pinch of the seed, as perhaps I c^d raise a few seedlings this autumn.³

I meant to have begun my letter by hearty rejoicing over Ayrton’s retirement. I hope his successor, Mr Adam, is a good sort of man; I never heard of him before.⁴

yours affectionately | Ch. Darwin