246 DROSERA ROTUNDIFOLIA. Cuar. & 
impulse in passing transversely across uearly the 
whole width of the disc had departed somewhat from 
a true course. This accords with what we have 
already seen of the impulse travelling less readily in 
a transverse than in a longitudinal direction. In 
some other cases, the exterior tentacles did not seem 
capable of such accurate movement as the shorter 
and more central ones. 
Nothing could be more striking than the appear- 
ance of the above four leaves, each with their ten- 
tacles pointing truly to the two little. masses of the 
phosphate on their discs. We might imagine that we 
were looking at a lowly organised animal seizing prey 
with its arms. In the case of Drosera the explanation 
of this accurate power of movement, no doubt, lies in 
the motor impulse radiating in all directions, and 
whichever side of a tentacle it first strikes, that side 
contracts, and the tentacle consequently bends towards 
the point of excitement. The pedicels of the tentacles 
are flattened, or elliptic in section. Near the bases of 
the short central tentacles, the flattened or broad face 
is formed of about five longitudinal rows of cells; in 
the outer tentacles of the disc it consists of about six 
or seven rows; and in the extreme marginal tentacles 
of above a dozen rows. As the flattened bases are 
thus formed of only a few rows of cells, the precision 
of the movements of the tentacles is the more remark- 
able ; for when the motor impulse strikes the base of 
a tentacle in a very oblique direction relatively to its 
broad face, scarcely more than one or two cells towards 
one end can be affected 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 
