Page:Life Movements in Plants.djvu/275

Rh records of the responsive reactions of various lights on growing organs. I shall now give records of the effect of various lights on the pulvinus of Mimosa piidica. The amplitude and time relations of the curves of response wiU giv3 a more precise idea of the quantitative effects of various lights in inducing excitation.

Actiim of white light : Exi)erime)it 95. — The sourca of light was an arc lamp ; a pencil of parallel light i^ made to pass through a trough of alum solution. This process of excluding thermal rays is adopted for the visible rays of the spectrum. Colour filters were also used for obtaining red, yellow and blue lights. The pencil of light is thrown upwards by an inclined mirror on the lower half of the pulvinus. The response is taken by an Oscil- lating recorder, giving successive dots at intervals of 10 seconds, the magnification employed being 100 times. The pulvinus being subjected to light for 10 seconds gave response by a fall of the leaf (Fig. 89). The response to light

EiCt 83— EfiEect |of white light on the pulvinus of .\rvnosa. Successive dots in this and in the following records are 'at intervals of 10'. (Magnification 100 times)

is thus found to be essentially similar to that induced by electric stimulus, the only difference being in the relative slugt'ishness of the reply. Electric shock passes instan- taneously through the mass of the pulvinus, stirring up