LEAP EXPOSURE TO SUN AND AIR. 



95 



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

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



Fig. 79. —Leaf Arrangement of Horse-chestnut on Vertical Shoots (top view). 



Pig. 80. —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 



