GROWTH SUBSTANCES FOR PHOTOTROPISM 



145 



20 40 60 80 lOO 120 140 160 180 200 



Fig. 46. — Course of curvature in different zones of the Avena eoleoptile after 

 phototropic stimulation with 50 m.c. for 10 seconds. Ordinate: size of curvature; 

 abscissa: time in minutes. Zone 1 is at the tip, zone 10 at the base. (From 

 Dolk, 19296.) 



