PHENOMENA OF PLANT-LIFE. 15 



These branches spread out in various directions, and attained 

 a length of six or eight inches. Each branch gradually 

 straightened out from the coil in which it first appeared, and 

 increased in length. When about two-thirds developed, it 

 began to revolve, so that its hooked tip described an ellipse 

 several inches in diameter. Its revolution was- made by a 

 series of bendings, in such a way as not to twist itself. The 

 tendrils moved in the same direction with the tip of the vine, 

 but somewhat irregularly both as to time and to the figure 

 described. During the day, the ellipse was broad, and at 

 night, long and narrow. Usually, the motion was scarcely 

 perceptible to the eye, but sometimes it moved two inches in 

 five minutes. The average time of revolution in November 

 was about three hours. If touched by the finger on the 

 sensitive or inner side, the tendril bent towards the place 

 where the finger was, and, not finding it, straightened itself 

 again. If, however, it came in contact with any object to 

 which it could cling, it bent at the point of contact, and the 

 concave curvature extended along the inside of the branch, 

 until the extremity was wound closely around the support. 

 Other branches would, also, fasten to the same object, if pos- 

 sible. The tendril, thus attached, increased in size and firm- 

 ness, and soon coiled upon itself in a double reversed spiral, 

 so as to exert a strain on the support. All the branches 

 having done this, they pull together and must fail together, 

 if at all. 



Another most obvious benefit derived from this double 

 spiral, is the elasticity of the fastening, which greatly dimin- 

 ishes the danger of rupture by violence. If the tendrils 

 of the squash failed in finding a support, the branches then 

 coiled upon themselves, and the main stalk often turned back 

 along the vine. 



The habits of climbing plants have been studied by Mr. 

 Charles Darwin and others ; but this field for research is by 

 no means exhausted. 



The tendrils of the grape vine are not very sensitive, but 

 fasten themselves very firmly to a suitable support. The 

 tendrils of the Coboea scandens are long, branching, and 

 tipped with woody claws. They are extensions of the petiole 

 of a compound leaf, revolve actively, and attach themselves 



