directly acted on. The stimulus proceeding from the glands of the disc
acts on the bending part of the [page 20] exterior tentacles, near
their bases, and does not (as will hereafter be proved) first travel up
the pedicels to the glands, to be then reflected back to the bending
place. Nevertheless, some influence does travel up to the glands,
causing them to secrete more copiously, and the secretion to become
acid. This latter fact is, I believe, quite new in the physiology of
plants; it has indeed only recently been established that in the animal
kingdom an influence can be transmitted along the nerves to glands,
modifying their power of secretion, independently of the state of the
blood-vessels.
The Inflection of the Exterior Tentacles from the Glands of the Disc
being excited by Repeated Touches, or by Objects left in Contact with
them.
The central glands of a leaf were irritated with a small stiff
camel-hair brush, and in 70 m. (minutes) several of the outer tentacles
were inflected; in 5 hrs. (hours) all the sub-marginal tentacles were
inflected; next morning after an interval of about 22 hrs. they were
fully re-expanded. In all the following cases the period is reckoned
from the time of first irritation. Another leaf treated in the same
manner had a few tentacles inflected in 20 m.; in 4 hrs. all the
submarginal and some of the extreme marginal tentacles, as well as the
edge of the leaf itself, were inflected; in 17 hrs. they had recovered
their proper, expanded position. I then put a dead fly in the centre of
the last-mentioned leaf, and next morning it was closely clasped; five
days afterwards the leaf re-expanded, and the tentacles, with their
glands surrounded by secretion, were ready to act again.
Particles of meat, dead flies, bits of paper, wood, dried moss, sponge,
cinders, glass, &c., were repeatedly [page 21] placed on leaves, and
these objects were well embraced in various periods from one hr. to as
long as 24 hrs., and set free again, with the leaf fully re-expanded,
in from one or two, to seven or even ten days, according to the nature
of the object. On a leaf which had naturally caught two flies, and
therefore had already closed and reopened either once or more probably
twice, I put a fresh fly: in 7 hrs. it was moderately, and in 21 hrs.
thoroughly well, clasped, with the edges of the leaf inflected. In two
days and a half the leaf had nearly re-expanded; as the exciting object
21