Action of blue light: Experiment 96.—Light was applied for 10 seconds and the amplitude of response was similar to that induced by white light (Fig. 90).
Fig. 90.—Effect of blue light on pulvinus of Mimosa.
Action of Ultra-violet rays: Experiment 97.—The source of light was a quartz mercury-vapour lamp. The effect was so intense that, to keep the record within the plate, I had to reduce the period of exposure to half, i.e., to five seconds. The responsive movement was initiated within six seconds of the application of light. The intensity and the rapidity of reaction is independently evidenced by the more erect curve of response (Fig. 91).
Fig. 91.—Effect of ultra-violet rays on the pulvinus of Mimosa.
Action of Infra-red rays: Experiment 98.—The obscure thermal rays also caused a strong excitatory reaction (Fig. 92). Attention is here drawn once more to the antagonistic reactions of temperature and radiation effects of heat.