17-1 REVIEWS. 



the tendrils were repeatedly drugged over each other ; but no 

 curvature ensued. I likewise repeatedly flirted small drops 

 of water from a brush on many tendrils, and syringed others 

 so violently that the whole tendril was dashed about, but they 

 never became curved. The impact from the drops of water 

 on my hand was felt far more plainly than that from the 

 loops of thread (weighing ^d of a grain) when allowed to 

 fall upon it, and these loops, which caused the tendrils to be- 

 come curved, had been placed most gently on them. Hence 

 it is clear, either that the tendrils are habituated to the touch 

 of other tendrils and to that of drops of rain, or that they are 

 sensitive only to prolonged though excessively slight pressure. 

 To show the difference of the kind of sensitiveness in different 

 plants, and likewise to show the force of the syringe used, I 

 may add that the lightest jet from it instantly caused the 

 leaves of the Mimosa to close; whereas the loop of thread 

 weighing gVd of a grain, when rolled into a ball and gently 

 placed in the glands at the base of the leaflets of the Mimosa, 

 caused no action." — (p. 90.) 



Of Cucurbitaceous tendrils, the most active, after those of 

 Sicyos (which Mr. Darwin has not observed), are those of 

 Echinocystis lobata. The internodes and tendrils revolve in 

 about an hour and three quarters, the former sweeping a circle 

 or ellipse of two or three inches in diameter, the latter often 

 one of 15 or 16 inches in diameter. Perhaps the most re- 

 markable appearance of discrimination in tendrils is that 

 which Mr. Darwin first noticed in this plant, but which may 

 be seen in others, — and which he thus describes : — 



"I repeatedly saw that the revolving tendril, though in- 

 clined during the greater part of its course at an angle of 

 about 45° (in one case of only 37°) above the horizon, in one 

 part of its course stiffened and straightened itself from tip to 

 base, and became nearly or quite vertical. . . . The tendril 

 forms a very acute angle with the extremity of the shoot, 

 which projects above the point where the tendril arises ; and 

 the stiffening always occurred 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 ten- 



