Cuap. IT. CLEMATIS. 57 
same general hook-like form as in C. viticella. The 
medial petiole and the lateral sub-petioles are sensitive, 
especially the much bent terminal portion. As the 
sensitiveness is here greater than in any other species 
of the genus observed by me, and is in itself remark- 
able, I will give fuller details. The petioles, when so . 
young that they have not separated from one another, 
are not sensitive; when the lamina of a leaflet has 
grown to a quarter of an inch in length (that is, about 
one-sixth of its full size), the sensitiveness is highest ; 
but at this period the petioles are relatively much 
more fully developed than are the blades of the leaves. 
Full-grown petioles are not in the least sensitive. A 
thin stick placed so as to press lightly against a 
petiole, having a leaflet a quarter of an inch in length, 
caused the petiole to bend in Shrs. 15m. In another 
case a petiole curled completely round a stick in 
12hrs. These petioles were left curled for 24 hrs., and 
the sticks were then removed; but they never 
straightened themselves. I took a twig, thinner than 
the petiole itself, and with it lightly rubbed several 
petioles four times up and down; these in 1 hr. 45 m. 
became slightly curled; the curvature increased during 
some hours and then began to decrease, but after 25 hrs. 
from the time of rubbing a vestige of the curvature re- 
mained. Some other petioles similarly rubbed twice, that 
is, once up and once down, became perceptibly curved 
in about 2 hrs. 30 m., the terminal sub-petiole moving 
more than the lateral sub-petioles; they all became 
straight again in between 12hrs. and 14hrs. Lastly, a 
