FIG. 35. Geotropic curvature of stems of Bryophyllum calycinum. These stems were 

 originally straight and suspended in a horizontal position. In about ten days they bent, 

 becoming concave on the upper side. - The black rings, made with india ink, which were 

 originally parallel, remain unaltered on the upper side of the stems, while their distance \ V 

 increases on the lower side, indicating that the curvature is due to an increase in growth ) " 

 on the lower side (of the cortex) of the stem. 



