i or Grypotherium domesticum. For a good account of
the discoveries see Smith Woodward in "Natural Science," XV., 1899, page
351, where the literature is given.)

LETTER 685. TO F. MULLER. Down, May 14th [1877].

I wrote to you a few days ago to thank you about Pontederia, and now
I am going to ask you to add one more to the many kindnesses which you
have done for me. I have made many observations on the waxy secretion on
leaves which throw off water (e.g., cabbage, Tropoeolum), and I am now
going to continue my observations. Does any sensitive species of Mimosa
grow in your neighbourhood? If so, will you observe whether the leaflets
keep shut during long-continued warm rain. I find that the leaflets open
if they are continuously syringed with water at a temperature of about
19 deg C., but if the water is at a temperature of 33-35 deg C., they
keep shut for more than two hours, and probably longer. If the plant is
continuously shaken so as to imitate wind the leaflets soon open. How is
this with the native plants during a windy day? I find that some other
plants--for instance, Desmodium and Cassia--when syringed with water,
place their leaves so that the drops fall quickly off; the position
assumed differing somewhat from that in the so-called sleep. Would you
be so kind as to observe whether any [other] plants place their leaves
during rain so as to shoot off the water; and if there are any such
I should be very glad of a leaf or two to ascertain whether they are
coated with a waxy secretion. (685/1. See Letters 737-41.)

There is another and very different subject, about which I intend to
write, and should be very glad of a little information. Are earthworms
(Lumbricus) common in S. Brazil (685/2. F. Muller's reply is given in
"Vegetable Mould," page 122.), and do they throw up on the surface of
the ground numerous castings or vermicular masses such as we so commonly
see in Europe? Are such castings found in the forests beneath the dead
withered leaves? I am sure I can trust to your kindness to forgive me
for asking you so many questions.

LETTER 686. TO F. MULLER. Down, July 24th, 1878.

Many thanks for the five kinds of seeds; all have germinated, and the
Cassia seedlings have interested me much, and I daresay that I shall
find something curious in the other plants. Nor have I alone profited,
for Sir J. Hooker, who was here on Sunday, was very glad of some of the
seeds for Kew. I am particularly obliged for