255 
of Rhythm in Plants. 
the clock had been stopped the plant gave evidence of an 
undoubted half-hourly rhythm. It is a most striking pheno- 
menon to observe. The plant seems to be impervious to the 
geotropic stimulus, and only when it has fulfilled the tendency 
to bend in one direction for half-an-hour does it reverse its 
movement and curve upwards. In Fig. i only a single reversal 
takes place ; no doubt when the alternation of the gravitation- 
stimulus ceases, the rhythm is soon destroyed ; but in other 
Fig. 2. 
cases, as we shall show, the impression on the plant is of 
longer duration. 
Fig. 2 is of interest as giving the termination of Experi- 
ment V, in which the movement was at first irregular. 
