254 DIONÆA MUSCIPULA. (Cuap. XIII. 
were next made in the same manner as before, one on each 
side of the base of a filament, on five distinct leaves, so that 
a little slip bearing a filament was connected with the rest 
of the leaf only at its two ends. These slips were nearly of 
the same size; one was carefully measured ; it was *12 of an 
inch (3:048 mm.) in length, and +08 of an inch (2-032 mm.) 
in breadth ; and in the middle stood the filament. Only one 
of these slips withered and perished. After the leaf had 
recovered from the operation, though the slits were still 
open, the filaments thus circumstanced were roughly touched, 
and both lobes, or one alone, slowly closed. In two instances 
touching the filament produced no effect; but when the 
point of a needle was driven into the slip at the base of the 
filament, the lobes slowly closed. Now in these cases the 
impuise must have proceeded along the slip in a line parallel 
to the midrib, and then have radiated forth, either from both 
ends or from one end alone of the slip, over the whole surface 
of the two lobes. 
Again, two parallel slits, like the former ones, were made, 
one on each side of the base of a filament, at right angles to 
the midrib. After the leaves (two in number) had recovered, 
the filaments were roughly touched, and the lobes slowly 
closed; and here the impulse must have travelled for a short 
distance in a line at right angles to the midrib, and then 
have radiated forth on all sides over both lobes. These 
several cases prove that the motor impulse travels, in all 
directions through the cellular tissue, independently of the 
course of the vessels. 
With Drosera we have seen that the motor impulse is 
transmitted in like manner in all directions through the 
cellular tissue; but that its rate is largly governed by the 
length of the cells and the direction of their longer axes. 
Thin sections of a leaf of Dionæa were made by my son, and 
the cells, both these of the central and of the more superficial 
layers, were found much elongated, with their longer axes 
directed towards the midrib; and it is in this direction that 
the motor impulse must be sent with great rapidity from one 
lobe to the other, as both close simultaneously. ‘I'he central 
parenchymatous cells are larger, more loosely attached 
together, and have more delicate walls than the more super- 
ficial cells. A thick mass of cellular tissue forms the upper 
surface of the midrib over the great central bundle of 
vessels. 
