. The doubt here expressed as to whether the result is due to
actual weight is interesting in connection with Pfeffer's remarkable
discovery that a smooth object in contact with the gland produces no
effect if the plant is protected from all vibration; on an ordinary
table the slight shaking which reaches the plant is sufficient to make
the body resting on the gland tremble, and thus produce a series of
varying pressures--under these circumstances the gland is irritated, and
the tentacle moves. See Pfeffer, "Untersuchungen aus d. bot. Institut
zu Tubingen," Volume I., 1885, page 483; also "Insectivorous Plants,"
Edition II., page 22.) The movement in this case does not depend on
the chemical nature of substance. Latterly I have tried experiments on
single glands, and a microscopical atom of raw meat causes such rapid
movement that I could see it move like hand of clock. In this case it
is the nature of the object. It is wonderful the rapidity of the
absorption: in ten seconds weak solution of carbonate of ammonia changes
not the colour, but the state of contents within the glands. In two
minutes thirty seconds juice of meat has been absorbed by gland and
passed from cell to cell all down the pedicel (or hair) of the gland,
and caused the sap to pass from the cells on the upper side of the
pedicel to the lower side, and this causes the curvature of the pedicel.
I shall work away next summer when Drosera opens again, for I am much
interested in subject. After the glandular hairs have curved, the oddest
changes take place--viz., a segregation of the homogeneous pink fluid
and necessary slow movements in the thicker matter. By Jove, I sometimes
think Drosera is a disguised animal! You know that I always so like
telling you what I do, that you must forgive me scribbling on my beloved
Drosera. Farewell. I am so very glad that you are going to reform your
ways; I am sure that you would have injured your health seriously. There
is poor Dana has done actually nothing--cannot even write a letter--for
a year, and it is hoped that in another YEAR he may quite recover.

After this homily, good night, my dear friend. Good heavens, I ought
not to scold you, but thank you, for writing so long and interesting a
letter.

LETTER 598. TO E. CRESY. Down, December 12th [1860?].

After writing out the greater part of my paper on Drosera, I thought of
so many points to try, and I wished to re-test the basis of one large
set of experiments,