ELECTRIC RESPONSE IN PLANTS 



decreased by '026 volt. A second and stronger tap 

 produced a second response, causing a greater diminu- 

 tion of P.D. by '047 volt (fig. 6, b). The accompanying 

 figure is a photographic record of another set of response- 

 curves (fig. 7). The first three responses are for a given 

 intensity of stimulus, and the next six in response to 

 stimulus nearly twice as strong. 

 It will be noticed that fatigue is 

 exhibited in these responses. Other '' 



A B 



"* Current of fruiiry 



^ tt-ction. Current, 



FIG. 6. (a) EXPERIMENT FOR EXHIBITING ELECTRIC EESPONSE IN PLANTS 

 BY METHOD OF NEGATIVE VARIATION, (b) BESPONSE IN LEAF-STALK 

 OF TURNIP TO STIMULI OF Two SUCCESSIVE TAPS, THE SECOND BEING 

 STRONGER. 



A and B contacts are about 2 cm. apart, B being injured. Plant is stimulated 

 by a tap between A and B. Stimulus acts on both A and B, but owing to 

 injury of B, effect at A is stronger and a negative variation due to differen- 

 tial action occurs. 



experiments will be described in the next chapter which 

 show conclusively that the response was not due to any 

 accidental circumstance but was a direct -result of 

 stimulation. But I shall first discuss the experimental 

 arrangements and method of obtaining these graphic 

 records. 



Response recorder. The galvanometer used is a 

 sensitive dead-beat D'Arsonval. The period of complete 

 swing of the coil under experimental conditions is about 

 11 seconds. A current of 10~ 9 ampere produces a 



c 2 



