Page:Life Movements in Plants.djvu/259

Rh As regards the action of light, the pulsation continued for a,time, even on the cessation of light. This per- sistence of autonomom activity increases with the intensity and duration of incident stimulus, that is to say with the amount Of incident energy. In the present ease a duration of ﬁve minutes’ exposure gave rise to a single pulsation, after which the movement of the leallet came to a stop. The next application lasted for ten minutes and this gave rise to four pulsations, two during application, and two after cessation of light. The next application ,was for forty-live minutes, and the pulsation persisted for nearly an hour after the cessation of light. The experiments on sub-tonic specimens show clearly that. the enerey supplied by the environment heci-mes as it were latent in the plant, increasing its potentiality for work.

The renewal of autonomous activity in a sub—tonic tissue. by the. action of external stimulus, will he found in every way parallel to the l'uiewal of growth in a sub-tonic organ.

Renew/(.1 of growth MIN/(’1' s/inm/us: [import/mm], .91.--” I ﬁnd that application of electric stimuhm paupws gmle in specimens whore, on account of extreme sub-tonicity growth has come to a state of standstill. The resumption of grOWth in grass haulms under the Stimulus “f gravity is a phenomenon probably connected with the almvp, '11“, causes which bring about cessation of growth in a mature organ are unknown; that there is a potentiality of growth even in a fully grown grass haultn is evidenced by the fact of its renewed growth under fresh stimulation. That this is not an exceptional phenomenon appears from the record which I obtained with a fully grown style of