186 TENDRILS. [CH. VIIl 



Bryonia as described inexp. 230. It will be found that 

 the tendrils show no signs of curving ; they must now be 

 touched with the uncoated part of the rod, to prove 

 that the absence of movement is not due to want of 

 sensitiveness. 



On a windy day (if the experiment is made out of 

 doors) it may be a little diflScult to make sure that, in the 

 first part of the experiment, the tendril does not come into 

 contact with the uncoated part of the rod : it is for this 

 reason that a good length of gelatine coating is recom- 

 mended. The tendril can however easily be held still by 

 touching its convex side with another gelatine rod; the 

 slight stickiness of the gelatine fixes the tendril while the 

 observer manipulates with the first rod. 



(233) Mimosa: movements produced by stimulation. 



The nature of the movements of Mimosa may be seen 

 by giving the plant a shake, when the main petioles will 

 be seen to sink, the secondary petioles to move together, 

 and the leaflets to close. If the plant is healthy, and is 

 in a moist atmosphere and at a temperature of at least 

 16° C, the leaves will rapidly recover their former position 

 and may again be irritated. 



An individual leaf may be made to move by gently 

 touching the pulvinus on the under side. Note that a 

 touch on the upper side has no such effect. The period 

 elapsing before the leaf recovers from the effect of the 

 touch varies with the temperature ; thus in one instance 

 a leaf recovered in 8 min. at 23° C; in from 12 — 15 min. 

 at 18°C. 



