1917] 



WEB— BR YOPII YLLUM 



45 



stems 



2 leaves at the basal node (fig. 29). All of the stems with the leaf 



(th 



unbent. 



afte 



remained 

 lavs. In 



Fig. 27 



time the bending of the stems with the leaf at the 

 apex proceeded and the stems assumed the typical 

 U-shape. The stems with the leaves at the base 

 remained unbent. The stems with the leaf at the 

 apex also formed roots (on the lower side of the 

 stem) ; the stems with leaves at the base formed 

 no roots or did not form them until much later. 



vii. Formation of roots in passively bent stems 



We have seen that in stems suspended horizontally the roots 

 have a tendency to form on the under side in the same region where 

 the bending occurs. They form also at the basal nodes, both the 

 upper and lower, but this fact does not concern us in this connec- 

 tion. The tendency of the roots to form on the lower side in that 

 region which becomes convex might suggest the possibility that 

 the root formation occurs in the convex region, not because it is 

 the lower side, but because the convexity in itself might in some 

 way favor root formation. The following experiment shows that 

 the roots form on the lower side of a stem regardless of whether this 

 lower side is concave or convex. 



