TORSIONAL RESPONSE 307 



flank. In the following experiments the pulvinus of Mimosa 

 was taken as the typical dorsi ventral organ. For lateral 

 stimulation, the plant is placed on its side, so that the vertical 

 lines of gravity impinge on one of the two flanks of the 

 organ. Two different positions, a and b, are distinguish- 

 able. In the a position the apex of the stem and the 

 upper half of the pulvinus are to the left of the observer, 

 and in the b position they are to the right. The arrange- 

 ment for taking a record of the torsional response in the 

 a position is shown in fig. 182. 



Torsional Response under Geotropic Stimulation 



Experiment 168. Torsional response. — When the leaf is 

 in a position, the geotropic torsion is in the direction of the 



Fig. 183. Fig. 184. 



Fig. 183. Torsional response under geotropic stimulation. 

 Clockwise torsion in a position is shown in the record as an 

 up-curve. (Mimosa.) 



Fig. 184. Anti-clockwise torsion in b position shown in the 



record as down-curve. 



In both these records there is a recovery on restoration of the 

 pulvinus to the normal position. The interval between two 

 thick dots represents duration of stimulation. 



movement of the hands of the clock. The clockwise torsion 

 induced is indicated in the record (fig. 183) as an up-curve ; 



