408 CH. XXXVI. TORSION UNDER UNILATERAL STIMULATION 



rate of positive torsion increased rapidly. At noon the 

 temperature rose to 42°, very much above the optimum, and 

 the retarding effect of the strong light was very great. The 



Fig. 223. Automatic record of diurnal variation of 



torsion. 



condition of drought caused by excessive transpiration also 

 conspired to induce a reversal of direction from positive 

 anti-clockwise to negative clockwise movement. This con- 

 tinued till 3 P.M., after which time the record shows a 

 repetition of what occurred 24 hours before. 



Effect of Unilateral Stimulation by Light 



In the previous chapter I described the effect of stimulation 

 by light applied simultaneously on all sides of an anisotropic 



