Cuar. & CONDUCTING TISSUES. 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, pos- 
sible 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 ten- 
tacles; it cannot, therefore, be sent along the fibro- 
- vascular bundles. The effect of cutting the central 
vessels, in the above cases, in preventing the transmis- 
sion 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 the motor impulse is not 
transmitted by the fibro-vascular bundles, is plainly 
confirmed ; and Professor Cohn has come to the same 
conclusion with respect to Aldrovanda—both members 
of the Droseracee. © 
As the motor impulse is not transmitted along the 
vessels, there remains for its passage only the cellular 
tissue; and the structure of this tissue explains to a 
certain extent how it travels so quickly down the long 
exterior tentacles, and much more slowly across the 
blade of the leaf. We shall also see why it crosseg 
