UNIVERSALITY OF SENSITIVENESS IN PLANTS 



31 



A to B, or away from the struck end. The intensity of the 

 current is determined by the height to which the struck end A 

 has been raised, and this again depends on the intensity of 

 the blow. Hence the intensity of the current is a measure 

 of the intensity of the stimulus or disturbance. The flow 

 subsides with the return of the pipe to its equilibrium posi- 

 tion. If the pipe had been disturbed throughout, the level 

 would have been raised equally at both ends, and there would 

 have been no flow. The object of the clamp is, therefore, to 

 confine the disturbance to one side. If the blow had been 



Fig. 22. Hydraulic Model for Explanation of Electric Response 



When an upstroke is given to A, a responsive current flows from A to B, 



and vice versa. 



given on the B side, the direction of the responsive flow would 

 have been reversed. 



The principle of electromotive response in plants is 

 exactly similar to this. The plant tissue is clamped at 

 c (fig. 23), and a stimulus is given at one end, say A. The 

 electrical level of that side is now found to be raised, it 

 becomes electro-positive, or like the copper in a voltaic com- 

 bination. The responsive current thus flows in the tissue 

 from A to 15, or away from the excited point. In the 

 external circuit containing the galvanometer, it flows, of 



