PHYSIOLOGY. BT. 
and surfaces with petioled glands, contract, accord 
ing to Roth’s observations, when stimulated, though 
very slowly. 
A species of filix in North America, the Onoclea 
sensibilis, has got this appellation merely from the 
circumstance, that its young leaves, when they begin 
to unfold themselves, shrink upon the least touch. 
The Nepenthes distillatoria, growing in Ceylon, has 
on the apex of its leaves a leaf-like ascidium, (§ 33), 
of which fig. 28 is a representation, which at times 
opens and closes, and even is filled with water. 
Of all plants, however, in that respect, the most 
singular is the Hedysarum gyrans, growing on the 
banks of the Ganges. It has trifoliate leaves, of . 
which the central one is larger than the two others. 
All these leaves move spontaneously. The large 
one rises backward up and down, the two smaller 
leaves at the sides have the same movement, only 
somewhat stronger. Laying hold of these leaves, 
and then removing the hand, quickens their motions, 
as if they were to make up for the lost time, till at 
last they return to their former slower motion. No 
particular stimulus seems to act on them, and they 
do not contract like other irritable plants. Nor 
does this motion of the leaves depend on sun light, 
for they move in light as well as in the dark, even 
when the leaves are perfectly asleep. It is besides 
remarkable, that the leaves in the height of erection, 
and during very warm but serene days, like the ani- 
mal muscular fibre, shew a tremulous motion. 
S 3 ey jo§. 279 
