1917] 



WEB— BR YOPH YLLUM 



3* 



obvious in r, figs. x. 4, 8, 0. and 



the second (and often the fourth) node 



>ic curvature also begins. This is 



When the leaf left 



base, the root formation is considerably less (as 

 curvature) , and what there is of root formation 



mam 



basal node 



When 



namely, 



base, root formation is more favored when the 



\ 



\ 



I 



1 



is below, as in figs, n, 12, and 13, than when it is 



appeared as yet in the leafless basal node on the 



upper 



series of experiments 



were started simultaneously. 



This tendency of the roots to form more easily 

 in the nodes of the under side of a horizontal stem 

 is an important link in the chain of circumstances 

 connecting root formation and geotropic curvature, since the 

 growth causing this curvature is confined to the cortex of the 

 under side of the stem. 



stems 



in. Experiments on stems split longitudinally 



order to find out the mechanism of geotropic curvature, 

 were split lengthwise and suspended horizontally in jars 



saturated with water vapor. Each half stem had 

 either at the apex or at the base. Figs. 14-20 gh 



the 



periments on the seventeenth 



