THE LATENT PERIOD 285 



the rate of growth, and thus tends to make that side 

 convex. There is thus an undue delay in the exhibition 

 of geotropic response by induced contraction of the excited 

 upper side. In these circumstances I tried to discover 

 specimens in which the geotropic action would be quick, 

 and in which the retarding effect of weight could be con- 

 siderablv reduced. 



Experiment 155. Geotropic response of the peduncle of 

 Tuberose. — For this I took a short length of peduncle of 



Fig. 166. 



Fig. 167. 



Fig. 166. Geotropic response of peduncle of Tuberose ; pre- 

 liminary down-movement is due to weight. 



Fig. 167. Geotropic response of petiole of Tropaeolum ; latent 

 period shorter than 20 seconds. 



Tuberose in a state of active growth ; the flower itself was 

 cut off in order to remove unnecessary weight. After 

 a suitable period of rest for recovery from the shock 

 of operation, the specimen was placed in a horizontal 

 position, and its record taken. The successive dots in the 

 curve are at intervals of 20 seconds, and the geotropic up- 

 movement is seen to be initiated (fig. 166) after the tenth 

 dot, the latent period being thus 3 minutes and 20 seconds, 

 the greater part of which was spent in recovering the 

 down-movement caused by the weight of the organ. 



