BENDING OF HIGHER PLANTS TOWARD THE LIGHT 73 



termed an optimum position. The reactions are adaptive. 

 In some instances if the Hght is too intense the chloroplasts 

 are found along the side walls which are more or less nearly 

 parallel with the incident rays. In others the leaves turn 

 so that the edge of the blade faces the light. In all proba- 

 bility both the petiole and the blade are sensitive to light, 

 at least in some leaves, but the method of regulating the 

 movements is still a mystery. 



