246 DEOSERA ROTUNDIFOLIA. CHAP. A, 



impulse in passing transversely across nearly 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 



