THE SPERMAPHYTES. 





!RSI' 

 253 



34. Study movements due to irritation. 

 a. Shake a flower pot in which a Sensitive Plant (Mi- 

 mosa pudica) is growing, and watch the movements of the 



FIG. 182. Leaf of the Sensitive Plant, Mimosa pudica. A, the ordinary day 

 position ; B, after irritation. (After Duchartre.) 



petioles, the secondary petioles, and the leaflets. Note the 

 time that elapses before the leaves return to their former 

 positions. Kepeat the shaking. Does the plant respond 

 to the irritation with the same 

 promptness ? Strike a sharp blow 

 with a pencil on a pair of ter- 

 minal leaflets. Observe that the 

 stimulus travels to the other leaf- 

 lets of the same leaf, and perhaps 

 even to other leaves. Touch in 

 succession with the sharp point of 

 a pencil the upper and the under 

 sides of the pulvinus. Does the 

 plant respond in either case ? This 

 plant may be grown from seed. 



b. Shake vigorously a flower pot containing plants of 

 Oxalis acetosella or Oxalis stricta. It may be necessary 

 to repeat. Vigorous irritation causes the leaflets to sink 



FIG. 183. Oxalis with leaves 

 in sleep position. (After 

 Hansen.) 



