LEAF EXPOSURE TO SUN AMD AlK. 



95 



leafy twig, bj^ a twisting about of the petioles. The adjust- 

 ment in the syringa, the maple, the horse-chestnut (Fig. 79), 



Pig. 79. —Leaf Arrangement of Horse-Chestnut on 'Wrtical Snoots (top view). 



Fig. ^. — Leaf Arrangement of Horse-chestnut on Vertical Shoots (side view). 



and many other opposite-leaved trees and shrubs, consists in 

 having each pair of leaves cover the spaces between the 



