PLANT RESPONSE 45 



a clamp between A and B, so that the disturbance may 

 not reach B. But we may get response even without 

 injury or block. If we have the contacts at A and B, 

 and if we give a tap nearer A than B (fig. 26, a), then 

 we have (1) the disturbance reaching A earlier than 

 B. (2) The disturbance reaching A is much stronger 

 than at B. The disturbance at B may be so comparatively 

 feeble as to be negligible. 



It will thus be seen that we might obtain responses 

 even without injury or block, in cases where the 

 disturbance is enfeebled in reaching a distant point. 

 In such a case on giving a tap near A a responsive 

 current would be produced in one direction, and in 

 the opposite direction when the tap is given near B 

 (fig. 26, b). Theoretically, then, we might find a 

 neutral point between A and B, so that, on originating 

 the disturbance there, the waves of disturbance would 

 reach A and B at the same instant and with the same 

 intensity. If, further, the rate of recovery be the same 

 for both points, then the electric disturbances produced 

 at A and B will continue to balance each other, and 

 the galvanometer will show no current. On taking a 

 cylindrical root of radish I have sometimes succeeded 

 in finding a neutral point, which, being disturbed, did 

 not give rise to any resultant current. But disturbing 

 a point to the right or to the left gave rise to opposite 

 currents. 



It is, however, difficult to obtain an absolutely 

 cylindrical specimen, as it always tapers in one direction. 

 The conductivity towards the tip of the root is not 

 exactly the same as that in the ascending direction. It 



