Chap. II. CLEMATIS. 07 



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 3 hrs. 15 m. In another 

 case a petiole curled completely round a stick in 

 12 hrs. These petioles were left curled for 21 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 12 hrs. and 14 hrs. Lastly, a 



