The Erectness of Plants. 



99 



How Leaves and Branches are Spread Out. 



Everyone knows that in addition to the more or less erect 

 main axis, stem and root, the plant also possesses stem-branches, 

 leaves and rootlets, all of which project at various angles from 

 the main axis. 



Taking the root-system first, we have the meristem in the 

 apex of the main root, the particles in some of the cells of which 

 may be considered as always in the process of " creaming." This, 

 in the vertical root (fig. 3, A), gives rise to what we may call a 

 normal polarity current," (that is a current produced by the 

 apical meristem, which flows along the cortex, but being sym 

 metricall> arranged it produces no curvature). In the lateral root 

 (fig. 3, B) a similar but smaller apical meristem produces an 



Fig. 3 — Diagram of root system to illustrate the orientation of the 

 secondary' root, B, by the balancing effect on the action current, 2, 1, 1, 0, 

 in it by tlie lea,k of normal polarity current froiii the niain root. A, at tliQ 

 point 1. 



