OBSERVATION BY RHEOTOME ON ELECTRIC RESPONSE 51 



It will be seen from the observations made on the first of 

 these two specimens that the maximum electro-motive effect 

 was attained in three-tenths of a second after excitation. In 

 the second case, the maximum was reached in two-tenths 

 of a second. The curve given in fig. 39 shows how quickly 

 the electro-motive variation attains a maximum, and how 

 rapid is its decline after reaching this point. There apppears 

 to be practically no latent period, the induction of the electro- 

 motive effect being apparently immediate. This will be 

 made evident by the results given in the next series. 



FIG. 39. Curve showing Rise and Fall of Responsive E.M. Change, 

 under moderate stimulation 



Ordinate represents galvanometric deflection ; abscissa, time. Large 

 division = I second. (Petiole of cauliflower. ) 



For the next experiment, I took the stem of Amaranth, 

 which I find to be more excitable and more quickly reacting 

 than the petiole of cauliflower. The intensity of stimulus 

 was here greater than in the last case. I may state now what 

 will be demonstrated in full later, that a strong stimulus 

 often gives rise, not to a single, but to multiple responses. 

 I had previously detected these multiple responses by means 

 of both mechanical and galvanometric indications, and found 

 them to have periodicities varying from some 1 5 seconds to 

 several minutes. Indeed, had they been muchr quicker than 

 they were, they could not have been detected, owing to the 



2 



