at first, and the contraction of these cells must draw the whole tentacle into the proper direction.  It is, perhaps, owing to the exterior pedicels being much flattened that they do not bend quite so accurately to the point of excitement as the [page 247] more central ones.  The properly directed movement of the tentacles is not an unique case in the vegetable kingdom, for the tendrils of many plants curve towards the side which is touched; but the case of Drosera is far more interesting, as here the tentacles are not directly excited, but receive an impulse from a distant point; nevertheless, they bend accurately towards this point.

Fig. 11. (Drosera rotundifolia.) Diagram showing the distribution of the vascular tissue in a small leaf.

On the Nature of the Tissues through which the Motor Impulse is Transmitted.—­It will be necessary first to describe briefly the course of the main fibro-vascular bundles.  These are shown in the accompanying sketch (fig. 11) of a small leaf.  Little vessels from the neighbouring bundles enter all the many tentacles with which the surface is studded; but these are not here represented.  The central trunk, which runs up the footstalk, bifurcates near the centre of the leaf, each branch bifurcating again and again according to the size of the leaf.  This central trunk sends off, low down on each side, a delicate branch, which may be called the sublateral branch.  There is also, on each side, a main lateral branch or bundle, which bifurcates in the same manner as the others.  Bifurcation does not imply that any single vessel divides, but that a bundle [page 248] divides into two.  By looking to either side of the leaf, it will be seen that a branch from the great central bifurcation inosculates with a branch from the lateral bundle, and that there is a smaller inosculation between the two chief branches of the lateral bundle.  The course of the vessels is very complex at the larger inosculation; and here vessels, retaining the same diameter, are often formed by the union of the bluntly pointed ends of two vessels, but whether these points open into each other by their attached surfaces, I do not know.  By means of the two inosculations all the vessels on the same side of the leaf are brought into some sort of connection.  Near the circumference of the larger leaves the bifurcating branches also come into close union, and then separate again, forming a continuous zigzag line of vessels round the whole circumference.  But the union of the vessels in this zigzag line seems to be much less intimate than at the main inosculation.  It should be added that the course of the vessels differs somewhat in different leaves, and even on opposite sides of the same leaf, but the main inosculation is always present.

Now in my first experiments with bits of meat placed on one side of the disc, it so happened that not a single tentacle was inflected on the opposite side; and when I saw that the vessels on the same side were all connected together by the two inosculations, whilst not a vessel passed over to the opposite side, it seemed probable that the motor impulse was conducted exclusively along them.