ELECTRIC RESPONSE 261 



after-effect was no longer a persistence of the negative 

 response, but disappearance of negativity and recovery to 

 zero-line of equilibrium at c (fig. 150). 



Fig. 149. Fig. 150. 



Fig. 149. Electric response of the petiole of Bryophyllum under 

 continuous photic stimulation. Increasing negativity repre- 

 sented by up-curve, neutralisation by down-curve. 



Fig. 150. Semi-diagrammatic representation of electric after- 

 effects due to photic stimulation. 



Pre-maximum stimulation, produced by stoppage of light at a, 

 gives rise to continuation of previous response followed 

 by recovery. 

 Stoppage of light at maximum, h, gives rise to recovery to equi- 

 librium position c. 

 Stoppage of light at post-maximum, c, gives rise to overshooting 

 below zero-line, as seen in the dotted record, c d. 



