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 same conclusion, namely that the motor impulse is not transmitted by the fibro-vascular bundles, is plainly confirmed; and Prof.  Cohn has come to the same conclusion with respect to Aldrovanda—­both members of the Droseraceae.