pedicels of the central tentacles, so that it is able to spread to a
considerable distance all round.
Whilst examining these leaves, I was struck with the fact that in six,
perhaps seven, of them the tentacles were much more inflected at the
distal and proximal ends of the leaf (i.e. towards the apex and base)
than on either side; and yet the tentacles on the sides stood as near
to the gland where the bit of meat lay as did those at the two ends. It
thus appeared as [page 237] if the motor impulse was transmitted from
the centre across the disc more readily in a longitudinal than in a
transverse direction; and as this appeared a new and interesting fact
in the physiology of plants, thirty-five fresh experiments were made to
test its truth. Minute bits of meat were placed on a single gland or on
a few glands, on the right or left side of the discs of eighteen
leaves; other bits of the same size being placed on the distal or
proximal ends of seventeen other leaves. Now if the motor impulse were
transmitted with equal force or at an equal rate through the blade in
all directions, a bit of meat placed at one side or at one end of the
disc ought to affect equally all the tentacles situated at an equal
distance from it; but this certainly is not the case. Before giving the
general results, it may be well to describe three or four rather
unusual cases.
[(1) A minute fragment of a fly was placed on one side of the disc, and
after 32 m. seven of the outer tentacles near the fragment were
inflected; after 10 hrs. several more became so, and after 23 hrs. a
still greater number; and now the blade of the leaf on this side was
bent inwards so as to stand up at right angles to the other side.
Neither the blade of the leaf nor a single tentacle on the opposite
side was affected; the line of separation between the two halves
extending from the footstalk to the apex. The leaf remained in this
state for three days, and on the fourth day began to re-expand; not a
single tentacle having been inflected on the opposite side.
(2) I will here give a case not included in the above thirty-five
experiments. A small fly was found adhering by its feet to the left
side of the disc. The tentacles on this side soon closed in and killed
the fly; and owing probably to its struggle whilst alive, the leaf was
so much excited that in about 24 hrs. all the tentacles on the opposite
side became inflected; but as they found no prey, for their glands did
216