78 



REGENERATION 



of the whole leaf. Figure 55 gives the curvature after 3 days, 

 the curvature being greater where the mass of the leaf was greater. 

 Figure 56 gives the curvature of the two half stems a day later, 

 and Fig. 57 on the sixth day. 



Fig. .58. — a, piece of stem with whole leaf; h, c, and d with increasingly reduced 

 leaf. Tl'ie geotropic curvature increases with mass of leaf. May 8 to 17. 



This experiment gives also an idea of the rapidity with which 

 the curvature occurs at the temperature of the greenhouse (about 

 24°C.). 



