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, 6). 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 
