TENDEIL-BEAREES. 75 



nearly or quite vertical. This occurred both when the supporting 

 internodes were free and when they were tied up; but was perhaps 

 most conspicuous in the latter case, or when the whole slioot hap- 

 pened to stand in an inclined position. The tendril forms a very 

 acute angle with the extremity of the shoot, which projects above 

 the point where the tendril arises j and the stiffening always oc- 

 curred as the tendril approached, and had to pass in its revolving 

 course, the point of difficulty— that is, the projecting extremity of 

 the shoot. Unless the tendril had the power of thus acting, it 

 would strike against the extremity of the shoot, and be arrested 

 by it. As soon as all three branches of the tendril have begun to 

 stiffen themselves in this remarkable manner, as if by a process of 

 turgescence, and to rise from an inclined into a vertical position, 

 the revolving movement becomes more rapid; and as soon as the 

 tendril has succeeded in passing the extremity of the shoot, its 

 revolWng motion, coinciding with that from gravity, often causes 

 it to fall into its previously inclined position so quickly, that the 

 end of the tendril could be distinctly seen travelling like the minute 

 hand of a gigantic clock. 



The tendrils are thin, from 7 to 9 inches in length, with a 

 pair of short lateral branches rising not far from the base. The 

 tip IS slightly but permanently curved, so as to act to a limited 

 extent as a hook. The concave side of the tip is highly sensitive 

 to a touch, but not so the convex side, as was likewise observed 

 by Mohl (S. 65) with other species of the family. I repeatedly 

 proved this difference by lightly rubbing four or five times the 

 convex side of one tendril, and only once or twice the concave side 

 of another tendril, and the latter alone curled inwards : in a few 

 hours afterwards, when those which had been rubbed on the con- 

 cave side had recovered themselves, I reversed the process of 

 rubbing, and always with a similar result. After touching the con- 

 cave side, the tip becomes sensibly curved in one or two minutes ; 

 and subsequently, if the touch has been at all rough, it becomes 

 coded into a helix. But this helix will, after a time, uncoil itself, 

 and be ready to act again. A loop of thin thread only one-sixteenth 

 of a grain in weight caused a temporary flexure in a tendril. One 

 pi my plants had two shoots near each other, and the tendrils 

 were repeatedly drawn across each other, but it is a singular fact 

 that they did not once catch each other. It would appear as if 

 the tendrils had become habituated to the contact of other tendrils, 

 for the pressure thus caused would apparently be greater than that 

 caused by a loop of soft thread weighing only the one-sixteenth 



