Chap. X.] 



CONDUCTING TISSUES. 



201 



These are shown in the accompanying sketch (Fig. 11) of a 

 small leaf. Little vessels from the neighboring bundles 

 enter all the many tentacles with which the surface is stud- 

 ded; 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. Bifur- 

 cation does not imply that 

 any single vessel divides, but 

 that a bundle divides into 

 two. By looking to either 

 side of the leaf, it will be 

 seen that a branch from the 

 great central bifurcation in- 

 osculates with a branch from 

 the lateral bundle, and that 

 there is a smaller inoscula- 

 tion between the two chief 

 branches of the lateral bun- 

 dle. The course of the ves- 

 sels 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 ves- 

 sels, 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 



Fig. 11. 

 (Drosera rotundifolia.) 

 Diagram showiDg the distribution 

 of the vascular tissue iu a small 

 leaf. 



decree nnnlojfons In constitution 

 and function to the nervous mat- 

 ter of nnlmnls. Now. that 

 through the researches of Gar- 

 diner ( Phil. Trans.' 18S.3) and 

 others the connection between 



plant-cells by Inter-cellular nroto- 

 ptasm has been establlsheu, we 

 can understand the trnnsmlKslon 

 of the motor Impulse as a molec- 

 ular change in the protoplasm 

 from cell to cell. F. D.] 



