REGENERATION IN PLANTS 



79 



do the leaf-buds, yet Vochting has found that the position in which 

 they appear varies with the position of the piece with respect to the 

 vertical. 



In the preceding cases the rudiments of the leaf-buds and of the 

 roots were probably present in most cases, so that gravity only 

 awakens them into activity. In other forms, as, for instance, in 



B 



FlG. 34. After Vochting. A. End of a piece of Heterocentron diversifolium. 

 B. Piece of same bent and suspended " with concave-side upward." 



Apex downward. 

 C. Piece of a stem of 



Salix viminalls. Apex upward. A piece of the side has been lifted up and two wedges 

 inserted. 



heterocentron, it is possible to show that gravity may even determine 

 the production of new buds. If pieces of the end of a branch, 

 including the growing point, are suspended vertically, some with the 

 apical end upward, others with the basal end upward (Fig. 34, A), 

 the former produce roots only around the base, but in the latter 

 roots appear frequently, not only at the base, but even extending 

 along the stem. They appear not only at the nodes, where pre- 



