seen, if a rather large bit of meat is placed on one side, the motor
impulse is sent, though slowly and imperfectly, in a transverse
direction across the whole breadth of the leaf. Nor can this latter
fact be accounted for by supposing that the transmission is effected
through the two inosculations, or through the circumferential zigzag
line of union, for had this been the case, the exterior tentacles on
the opposite side of the disc would have been affected before the more
central ones, which never occurred. We have also seen that the extreme
marginal tentacles appear to have no power to transmit an impulse to
the adjoining tentacles; yet the little bundle of vessels which enters
each marginal tentacle sends off a minute branch to those on both
sides, and this I have not observed in any other tentacles; so that the
marginal ones are more closely connected together by spiral vessels
than are the others, and yet have much less power of communicating a
motor impulse to one another.
But besides these several facts and arguments we have conclusive
evidence that the motor impulse is not sent, at least exclusively,
through the spiral vessels, or through the tissue immediately
surrounding them. We know that if a bit of meat is placed on a gland
(the immediately adjoining ones having been removed) on any part of the
disc, all the short sur- [page 251] rounding tentacles bend almost
simultaneously with great precision towards it. Now there are tentacles
on the disc, for instance near the extremities of the sublateral
bundles (fig. 11), which are supplied with vessels that do not come
into contact with the branches that enter the surrounding tentacles,
except by a very long and extremely circuitous course. Nevertheless, if
a bit of meat is placed on the gland of a tentacle of this kind, all
the surrounding ones are inflected towards it with great precision. It
is, of course, possible that an impulse might be sent through a long
and circuitous course, but it is obviously impossible that the
direction of the movement could be thus communicated, so that all the
surrounding tentacles should bend precisely to the point of excitement.
The impulse no doubt is transmitted in straight radiating lines from
the excited gland to the surrounding tentacles; it cannot, therefore,
be sent along the fibro-vascular bundles. The effect of cutting the
central vessels, in the above cases, in preventing the transmission of
the motor impulse from the distal to the basal end of a leaf, may be
attributed to a considerable space of the cellular tissue having been
divided. We shall hereafter see, when we treat of Dionaea, that this
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