MOVEMENT IN PLANTS. 243 



seconds in Cyclanthera, thirty seconds in Sicyos, one to 

 two minutes in Bryonia. Stimulate the tendril more 

 strongly e.g. by drawing it between the fingers : it be- 

 comes rolled up more completely. After slight stimulation 

 just sufficient for the formation of a complete ring the 

 tendril soon begins to straighten again, though the undoing 

 of the curvature takes considerably longer than its formation, 

 e.g. about 25 to 30 minutes in Cyclanthera. 



333. Distinction between Sensitiveness and Re- 

 sponsiveness. Show by experiments that (1) if the 

 reacting side of a tendril is touched with a stick at two 

 places, say 1 to 2 cm. apart, two curvatures result, the 

 region between remaining straight ; (2) if the tendril 

 is stimulated first on the upper side and then on the lower 

 side, no curvature takes place provided the two stimuli be 

 equal ; (3) if a part of the upper side and at the same time 

 the whole of the lower side be stimulated, curvature occurs 

 only at the place on the lower side which lies opposite the un- 

 stimulated regions of the upper side. From these results 

 it follows that the apparently insensitive upper side is 

 really as sensitive as the lower, but that stimulation of the 

 upper side either produces no visible result, or else simply 

 inhibits curvature on the lower side. 



334. Tendrils respond only to Stimulation by 

 Solids. Prove by experiments that (1) extremely small 

 and light objects, like very small pieces of thread, cause 

 curvature when placed on the tip of a tendril ; (2) a shoot 

 of Sicyos, etc., may be violently shaken, yet only slight 

 responses are made so long as the tendrils are not allowed 

 to come into contact with any obstacle ; (3) a jet of water 

 may be directed against the reacting region by means of 

 a syringe or wash-bottle or by holding the tendril under 

 a running tap, without causing curvature ; (4) water into 

 which a little chalk has been stirred causes stimulation at 

 once. Hence neither friction with the air nor the falling 

 of rain will act as stimuli, and a tendril can apparently dis- 

 tinguish between liquids and solids, even when the latter 

 are present as small suspended particles in water, 



