
BEHAVIOUR OF PLANTS TOWARD LIGHT 149 
. mosaic.” Then on the edge of the wood or grove you 
can study many examples of the effect of light on the 
unequal growth of the branches of trees and shrubs. 
What advantage to the plant comes from this power 
to turn the leaves so as to face the light? What plant 
food can be formed only in the green leaves in the 

Fic, 184. Spray of leaves of striped maple, showing different 
lengths of leafstalks. 
presence of light? What economy is there in the 
plant's having broad and thin leaves, instead of having 
the same amount of tissue in a rounded green mass? 
Why do trees on the edge of a wood, or of a grove, 
have more and longer branches on the side away from 
other trees than on the side next the forest? In leaf 
clusters on branches why are some of the leafstalks 
much longer than others (see Fig. 184)? 





