Page:Life Movements in Plants.djvu/271

Rh growing organ, I give a record (Fig. 88) obtainel with a

Fig. 88.— Cintractile response of yrowitig organ under electric shock. Succes- sive dot? at intervals of -1". Vertical lines below represent intervals of one minute. (Magn tication 1,000 time.-.)

growing bud of Cnniini under the stimulus of electric shock above the critical intensity. The recorder gave a magnifica- tion of a thousand times. In Fig. 88, the normal growth elongation is represented as a down-curve. On the applica- tion of stimulus the normal expansion was suddenly reversed to excitatory contraction, the latent period of reaction was one second and the period of the attainment of maximum contraction (apex-time) was 4 minutes. The orgaij re- covered its original length after a further period of seven minutes and then continued its natural growth elongation. Repetition of stimuli gave rise to successive contractile responses which are in every way similar to the mechanical responses of Mimosa piidica. The essential similarity of