THE LEAF 247 
Gross Structure AND Hisrorocy or DirreERENT TYPES OF 
DorsIVENTRAL LEAF BLApEs.—1. DorsIVENTRAL UMBROPHYTIC. 
Characterized by leaves mostly undivided and having the largest 
and most continuous leaf expanse. Usually the deepest green 
leaves we have, to enable the leaves to absorb scattered and 
reduced rays that pass in through high trees and shrub overhead. 
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- Their texture is usually thin and soft. In microscopic structure 
they are covered with a cutinized epidermis which has all the 
stomata on the lower surface. The chlorenchyma is fairly 
spongy, the spongy parenchyma having decided intercellular 
spaces. Examples: Hydrastis, Asarum, Maranta. 
2. DorsIVENTRAL Mesopuytic.—In this type of dorsi- 
ventral leaf there is a tendency to subdivision, either to slight or 
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