Cuar. X.] CONDUCTING TISSUES. 203 
a transverse direction across the whole breadth of the leaf. 
Nor can this latter fact be accounted for by supposing that 
the transmission is affected through the two inosculations, vr 
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 com- 
municating 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 surrounding 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 sur- 
rounding 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. Itis, 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 trans- 
mitted 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 Dionza, that this same conclusion, namely that. 
