456 LIFE MOVEMENTS IN PLANTS 



when the lower half of the organ occupied the favour- 

 able up-position. This will be seen from the results of 

 two typical experiments in table given above. 



The electrical mode of investigation thus leads to con- 

 firm the result obtained with mechanical method that the 

 lower half of the pulvinus of Mimosa is geotropically 

 more excitable than the upper half. 



RELATION BETWEEN ANGLE OF INCLINATION AND 

 GEOTROPIC EFFECT. 



In the Method of Axial Rotation, the condition of the 

 experiment is ideally perfect ; in the neutral position the 

 sides A and B are both parallel to the vertical lines of 

 gravity, and are little affected by geotropic reaction. As 

 the specimen is rotated on its long axis the vertical com- 

 ponent of the force of gravity increases with the angle of 

 inclination. The hypothetical statolithic particles will be- 

 come displaced all along the cell, and the vertical pressure 

 exerted by them will also increase with the angle. 



The geo-electric response will then afford us a measure 

 of the intensity of excitation induced at various angles of 

 inclination. The mechanical response on account of its 

 inherent defects does not afford us the true relation be- 

 tween the angle of inclination and intensity of geotropic 

 reaction. But the electric method of inquiry is free from 

 the defects of the mechanical method. 



Expenment 176. — The specimen was rotated so that the 

 angle of rotation was 45°, and the maximiim electric 

 response observed. The angle was next increased to 90^ 

 and the reading for the enhanced response taken. The 

 ratio of the geo-electric response at 90° and 45°, thus 

 affords us a measure of the effective stimulations at the 



