56 LEAF-CLIMBERS. Cuap. IL 
this latter species it has diminished in the basal part 
of the main petiole, in which alone it resided in C. 
montana; whilst it has increased in the abruptly bent 
terminal portion. 
Clematis lammula.—The rather thick, straight, and 
stiff shoots, whilst growing vigorously in the spring, 
make small oval revolutions, following the sun in their 
course. Four were made at an average rate of 3 hrs. 
45m. The longer axis of the oval, described by the 
extreme tip, was directed at right axigles to the line 
joining the opposite leaves; its length was in one case 
only 13, and in another case 1$ inch; so that the 
young leaves were moved a very short distance. The 
shoots of the same plant observed in midsummer, 
when growing not so quickly, did not revolve at all. 
I cut down another plant in the early summer, so that 
by August Ist it had formed new and moderately 
vigorous shoots; these, when observed under a bell- 
glass, were on some days quite stationary, and on 
other days moved to and fro only about the eighth of 
an inch. Consequently the revolving power is much 
enfeebled in this species, and under unfavourable cir- 
cumstances is completely lost. The shoot must depend 
for coming into contact with surrounding objects on the 
probable, though not ascertained spontaneous move- 
ment of the leaves, on rapid growth, and on movement . 
from the wind. Hence, perhaps, it is that the petioles 
have acquired a high degree of sensitiveness as a com- 
pensation for the little power of movement in the shoots, 
The petioles are bowed downwards, and have the 
