540 LIFE MOVEMENTS IN PLANTS 



The experiments that have just been described on 

 the effects of rise of temperature, and of light, show 

 that they are antagonistic to each other. In the forenoon 

 the opening movement under light has to be carried out 

 against the closure movement due to rise of temperature. 

 Light, therefore, is the predominant factor in the diurnal 

 movement of the leaflets of Cassia. The closure effect 

 of darkness at night, on the other hand, overpowers the 

 tendency of movement of opening due to fall of temperature. 



DIURNAL MOVEMENT OF THE LEAFLET OF Oassia alata. 



Experiment 206. — I next obtained the diurnal record of 

 the leaflet, from 4 p.m. till 1 p.m. next day. The leaflets 

 remain open from 1 p.m. to 4 p.m. and the record of 

 this period is therefore omitted. In the diurnal record 



FKt. 1!I2. — Diurnal movement of the leaflet of Cassia alata. Closure movement 

 commenced at 5 p.m. and completed by '.Ip.m. Leaflets began to open at 5 a.m. 



(Fig. 192) the first thick dot was made at 4 p.m. and 

 successive thick clots are at intervals of an hour, the 



