_Pre-maximum after-effect: Experiment 217._--Light was allowed to act on the upper half of the pulvinus for two minutes and twenty seconds; this induced an up-movement _i.e._, a positive curvature. On the stoppage of light the up-movement continued for one minute and twenty seconds, after which the down-movement of recovery was completed in six minutes and twenty seconds (Fig. 207). The immediate after-effect is thus a movement upward, away from the zero line of equilibrium. The result is seen to be the same as the electric after-effect of pre-maximum stimulation. [Illustration: FIG. 207.--Light applied at arrow, and stopped at the second arrow within a circle. After-effect of pre-maximum stimulation is continuation of positive curvature followed by recovery.] [Illustration: FIG. 208.--After-effect at maximum; recovery towards zero position of equilibrium.] [Illustration: FIG. 209.--After-effect at post-maximum is a rapid overshooting below the position of equilibrium. Light was applied in all cases on upper half of pulvinus of terminal leaflet of _Desmodium gyrans_.] _After-effect at maximum: Experiment 218._--Application of light for 5 minutes and twenty seconds induced a maximum positive curvature. Stoppage of light was followed at once by recovery which was completed in about 10 minutes (Fig. 208). _After-effect at post-maximum: Experiment 219._--As the plant was fatigued by previous experiments, a fresh specimen was taken and light was applied continuously on the upper half of the pulvinus. This gave rise first to a maximum positive curvature, subsequently diminished by transverse transmission of excitation. Neutralisation took place after application of light for 17 minutes. On the stoppage of light, there was a sudden overshooting _below_ the zero line (Fig. 209), and the rate of the movement on the cessation of light was nearly twice as quick as during the process of neutralisation. SUMMARY. The after-effect of light is modified by the duration of exposure to light. Under continued action of light, the electric response of galvanometric negativity in plants attains a maximum after which it undergoes decline, and neutralisation. The electrical after-effect exhibits characteristic differences depending on the duration of previous exposure to light. The pre-maximal after-effect is a temporary continuation of response under light followed by recovery. The after-effect at the maximum is a recovery to the normal equilibrium. The after-effect at post-maximum is an 'overshooting' below the position of equilibrium. The immediate and after-tropic response of light are similar to the corresponding photo-electric effects. The pre-maximum after-effect is a continuation of positive tropic movement followed by recovery; the after-effect at maximum is a recovery to the normal equilibrium position of the organ. The post-maximum after-effect is an overshooting below the position of normal equilibrium.