44 RESPONSE IN THE LIVING AND NON-LIVING 
CELA TE aye 
PLANT RESPONSE—ON DIPHASIC VARIATION 
Diphasic variation—Positive after-effect and positive response— 
Radial E.M. variation. 
WuHEN a plant is stimulated at any point, a mole- 
cular disturbance—the excitatory wave—is propagated 
outwards from the point of its initiation. 
Diphasic variation.—This wave of molecular dis- 
turbance is attended by a wave of electrical disturb- 
ance. (Usually speaking, the electrical relation between 
disturbed and less disturbed is that of copper to zinc.) 
It takes some time for a disturbance to travel from 
one point to another, and its intensity may undergo 
a diminution as it recedes further from its pomt of 
origin. Suppose a disturbance originated at C; if two 
points are taken near each other, as A and B, the 
disturbance will reach them almost at the same time, 
and with the same intensity. The electric disturbance 
will be the same in both. The effect produced at A 
and B will balance each other and there will be no 
resultant current. 
By killing or otherwise reducing the sensibility of B 
as is done in the method of injury, there is no response 
at B, aud we obtain the unbalanced response, due to 
disturbance at A; the same effect is obtained by putting 
