144 TENDEIL-BEABEES. Chap. IV. 



sensitive, for a slight rubbing produced no effect, al- 

 though prolonged contact with a stick caused it to bend. 

 The two branches are sensitive on all sides, so that they 

 converge if touched on their inner sides, and diverge 

 if touched on their outer sides. If a branch be touched 

 at the same time with equal force on opposite sides, 

 both sides are equally stimulated and there is no move- 

 ment. Before examining this plant, I had observed 

 only tendrils which are sensitive on one side alone, 

 and these when lightly pressed between the finger and 

 thumb become curved; but on thus pinching many 

 times the tendrils of the Cissus no curvature ensued, 

 and I falsely inferred at first that they were not at all 

 sensitive. 



Cissus aniarctious. — The tendrils on a young plant 

 were thick and straight, with the tips a little curved. 

 When their concave surfaces were rubbed, and it was 

 necessary to do this with some force, they very slowly 

 became curved, and subsequently straight again. 

 They are therefore much less sensitive than those of 

 the last species ; but they made two revolutions, fol- 

 lowing the sun, rather more rapidly, viz., in 3 hrs. 30 m. 

 and 4 hrs. The internodes do not revolve. 



Ampelopsis hederacea {Virginian Creejaer). — The inter- 

 nodes apparently do not move more than can be 

 accounted for by the varying action of the light. The 

 tendrils are from 4 to 5 inches in length, with the main 

 stem sending off several lateral branches, which have 

 their tips curved, as may be seen in the upper figure 

 (fig. 11). They exhibit no true spontaneous revolving 



