not acted on by gravitation or other
irritants, such as contact, etc., etc., but a new tip is regenerated
in from two to four days, and then the radicle is again acted on by
gravitation, and will bend to the centre of the earth. The tip of the
radicle is a kind of brain to the whole growing part of the radicle!
(757/5. We are indebted to Mr. Archer-Hind for the translation of the
following passage from Plato ("Timaeus," 90A): "The reason is every
man's guardian genius (daimon), and has its habitation in our brain; it
is this that raises man (who is a plant, not of earth but of heaven) to
an erect posture, suspending the head and root of us from the heavens,
which are the birthplace of our soul, and keeping all the body upright."
On the perceptions of plants, see "Nature," November 14th, 1901--a
lecture delivered at the Glasgow meeting of the British Association by
Francis Darwin. See also Bonitz, "Index Aristotelicus," S.V. phuton.)

My observation will be published in about a week's time, and I would
have sent you the book, but I do not suppose that there is anything else
in the book which would interest you. I am delighted that you have
drawn attention to galls. They have always seemed to me profoundly
interesting. Many years ago I began (but failed for want of time,
strength, and health, as on infinitely many other occasions) to
experimentise on plants, by injecting into their tissues some alkaloids
and the poison of wasps, to see if I could make anything like galls.
If I remember rightly, in a few cases the tissues were thickened and
hardened. I began these experiments because if by different poisons I
could have affected slightly and differently the tissues of the same
plant, I thought there would be no insuperable difficulty in the fittest
poisons being developed by insects so as to produce galls adapted for
them. Every character, as far as I can see, is apt to vary. Judging from
one of your sentences you will smile at this.

To any one believing in my pangenesis (if such a man exists) there does
not seem to me any extreme difficulty in understanding why plants have
such little power of regeneration; for there is reason to think that
my imaginary gemmules have small power of passing from cell to cell.
(757/6. On regeneration after injury, see Massart, "La Cicatrisation
chez les Vegetaux," in Volume 57 (1898) of the "Memoires Couronnes,"
published by the Royal Academy of Belgium. An account of the literature
is g