84 MB. DABWIH 0> T CLIMBING PLANTS. 



examining this plant, I had observed only those tendrils which 

 are sensitive on one side, and these when lightly pressed between 

 the finger and thumb become curved ; but on thus pinching many 

 times the tendrils of this Cissus no curvature ensued, and 1 was at 

 first falsely led to infer that they were not at all sensitive to a touch. 



Cissus antarcticus. — The tendrils on a young plant were thick 

 and straight, with the tips a little curved ; when the concave sur- 

 face was rubbed with some force they very slowly became curved, 

 and subsequently became straight again. Hence they are much 

 less sensitive than the tendrils of the last species; but they made 

 two revolutions, following the sun, rather more rapidly, viz. in 

 3 h. 30 m. and A h. The internodes do not revolve. 



Ampeiopsis hederacea, or Virginian Creeper. — In this plant 

 also the internodes do not move more than apparently can he 

 accounted for by the varying action of the light. The tendrils arc 

 from 4 to 5 inches in length ; the main stem sends off several 

 lateral branches, which have their tips curved, as may be seen in 

 fig. 11, A. They exhibit no true spontaneous revolving move- 

 ment, but turn, as was long ago observed by Andrew Knight*, 

 from the light to the dark. I have seen several tendrils move 

 through an angle of 180° to the dark side of a case in less than 

 24 hours ; but the movement is sometimes very much slower. 

 The several lateral branches often move independently of each 

 other, and sometimes irregularly, without any apparent cause. 

 These tendrils are less sensitive to a touch than any others ob- 

 served by me : by gentle but repeated rubbings with a twig, the 

 lateral branches, but not the main stem, became in the course of 

 three or four hours slightly curved ; but they seemed to have 

 hardly any power of again straightening themselves. The tendrils 

 of a plant which crawled over a large box-tree clasped several of 

 the branches. But I have repeatedly seen the tendrils come into 

 contact with sticks, and then withdraw from them. When they 

 meet with a flat surface of wood, or a wall (and this is evidently 

 what they are adapted for), they turn all their branches towards it, 

 and, spreading them widely apart, bring their hooked tips laterally 

 into contact with it. In cftecting this, the several branches, after 

 touching the surface, often rise up, place themselves in a new 

 position, and again come down into contact with it. 



In the course of about two days after a tendril has arranged its 

 branches so as to press on any surface, the curved tips swell, 

 become bright red, and form on their under-sides the well-known 

 * Trans. Phil. Soc. 1812, p. 314. 



