PLANT CURRENTS 



15 



voLt - 



O-O>- 



voLC 

 010- 



2 



70 



2O m. 



FIG. 5. Vine-shoot. Electrical Effects of Mechanical Excitation 

 (10 centigrammetres) before and after boiling. 



The first four excitations (before boiling) give responses of 0.060, 0.045, 0.045, 

 0.040 volt. The 5th, 6th, and 7th excitations (after boiling) give no response. 



The deflection preceding the ist excitation is by 0.04 volt, and the resistance of the 

 stem between leading-off electrodes was 500,000 ohms. The deflection preceding 

 the 5th excitation is by o.oi volt, and the resistance of the boiled stem was 

 60,000 ohms. 



FIG. 6. Experiment (3023). Bean-Radicle (Phaseolus) 3 inches 



long and quite etiolated, incubated in the dark at 25 for five days. Led 

 off to recording galvanometer by two unpolarisable electrodes, A and 

 B. The radicle is struck transversely near A, then near B, by a bristle 

 fixed to the end of a revolving rod. In each case the deflection is such 

 as to indicate that the struck spot is rendered electropositive (galvano- 

 metrically negative) to the unstruck spot. The effects are completely 

 abolished by strong tetanisation. 



