220 



EXPERIMENTS WITH PLANTS 



^^^^pp' What are the most perfect leaf- 



igt^T^ mosaics you can find? 



Notice the difference between 

 the arrangement of leaves on hori- 

 zontal and vertical shoots of the 

 same plants (see Figs. 128, 129 and 

 130). Which arrangement re- 

 quires the greatest bending and 

 twisting of the leaves out of their 

 original position? 



In what part of the leaf is the 

 mechanism located by which these 

 bending and twisting movements 

 are accomplished? Study espe- 

 cially in this respect the leaves 

 of the Scarlet Eunner or other 

 bean, and examine the cushion- 

 like swelling at the base of the stalk of each leaf and 

 leaflet. 



Inasmuch as a tree forms its branches and leaves 

 with reference to the light, prevail- 

 ing winds, etc., it follows that when 

 it is transplanted its orientation 

 should not be changed, i. e., the 

 same side should be toward the north 

 both before and after planting. 



129. Appearance of the 



Study both trees and shrubs (the branch shown in rig. 



n ■, . n\xT 128 when viewed from 



smaller plants as well), to discover above. 



128. Upright branch of Peri 

 winkle ( Vinca). 



