ELECTRIC RESPONSE IN PLANTS 25 
vibration. It is of course obvious that if the length 
of the specimen be doubled, the vibration, in order 
to produce the same effect, must be through twice the 
angle. I took a leaf-stalk of turnip and fixed it in the 
torsional vibrator. I then took record of responses to 
two successive taps, the intensity of one being nearly 
double that of the other. Having done this, I applied 
to the same stalk two successive torsional vibrations of 
45° and 67° respectively. These successive responses 
o b Cc d 

O05 volt 
Current. of Injury 

Fic. 12.—REsPoNSE IN PLANT TO Mecuanicat Tap oR VIBRATION 
The end B is injured. A tap was given between A and B and this 
gave the response-curve a. A stronger tap gave the response b. 
By means of the handle H, a torsional vibration of 45° was now 
imparted, this gave theresponsec. Vibration through 67° gave d. 
to taps and torsional vibrations are given in fig. 12, 
and from them it will be seen that these two modes 
of stimulation may be used indifferently, with equal 
effect. The vibrational method has the advantage over 
tapping, that, while with the latter the stimulus is 
somewhat localised, with vibration the tissue subjected 
to stimulus is uniformly stimulated throughout its 
length. 
Effectiveness of stimulus dependent on rapidity also. 
In order that successive stimuli may be equally effective 
