80 



REGENERATION 



In all the experiments thus far discussed the leaf was at the apex 

 of the stem. When the leaf is at the base of a piece of stem the 

 curvature occurs also though the rate of curvature is apparently 

 less for the same mass of leaf than if the leaf is at the apex. 

 When the leaf is in the middle of the stem the curvature occurs 

 chiefly in the basal part of the stem. 



Fig. 60. 



Fig. 61. 

 Figs. 60 and 61. — Stem split longitudinally, each half having a leaf at the 

 apex. The stems were suspended horizontally in moist air, one with the cortex 

 below (Fig. 60), the other with the cortex above (Fig. 61). Only the half stem 

 with the cortex below (Fig. 60) bends. 



3. Mechanism of Geotropic Curvature in Bryopkyllum caly- 

 cinum. — In order to find out the mechanism of the geotropic 

 curvature experiments were made with stems spht longitudi- 



