epenthes, and I hope
that you will have good luck. It is good news that the fluid is acid;
you ought to collect a good lot and have the acid analysed. I hope
that the work will give you as much pleasure as analogous work has me.
(719/1. Hooker's work on Nepenthes is referred to in "Insectivorous
Plants," page 97: see also his address at the Belfast meeting of the
British Association, 1874.) I do not think any discovery gave me more
pleasure than proving a true act of digestion in Drosera.

LETTER 720. TO J.D. HOOKER. Down, November 24th, 1873.

I have been greatly interested by Mimosa albida, on which I have been
working hard. Whilst your memory is pretty fresh, I want to ask a
question. When this plant was most sensitive, and you irritated it, did
the opposite leaflets shut up quite close, as occurs during sleep, when
even a lancet could not be inserted between the leaflets? I can never
cause the leaflets to come into contact, and some reasons make me doubt
whether they ever do so except during sleep; and this makes me wish much
to hear from you. I grieve to say that the plant looks more unhealthy,
even, than it was at Kew. I have nursed it like the tenderest infant;
but I was forced to cut off one leaf to try the bloom, and one was
broken by the manner of packing. I have never syringed (with tepid
water) more than one leaf per day; but if it dies, I shall feel like a
murderer. I am pretty well convinced that I shall make out my case of
movements as a protection against rain lodging on the leaves. As far as
I have as yet made out, M. albida is a splendid case.

I have had no time to examine more than one species of Eucalyptus. The
seedlings of Lathyrus nissolia are very interesting to me; and there is
something wonderful about them, unless seeds of two distinct leguminous
species have got somehow mingled together.

LETTER 721. TO W. THISELTON-DYER. Down, December 4th, 1873.

As Hooker is so busy, I should be very much obliged if you could give
me the name of the enclosed poor specimen of Cassia. I want much to
know its name, as its power of movement, when it goes to sleep, is very
remarkable. Linnaeus, I find, was aware of this. It twists each separate
leaflet almost completely round (721/1. See "Power of Movement in
Plants," Figure 154, page 370.), so that the lower surface faces the
sky, at the same time depressing them all. The terminal leaflets are
pointed towards the base of the leaf. The whole leaf is als