KEY TO GENERA AND SPECIES 



55 



100. Leaf-stalk prominently flattened in a plane 

 at right angles to the blade 101. 



100. Leaf-stalk not flattened, or but very slightly 



104. 



101. Blade triangular, triangularly egg-shaped, or 



rhombic 102. 



1 01. Blade from broad heart-shaped or rounded to 

 lance-shaped or oblong, usually pointed. 



Fig. 97. 

 Lombardy Poplar. 



Fig. 98. 

 Carolina Poplar. 



Penn. northward and westward. (Fig. 96.) 

 American Aspen, Quaking Asp, Trem- 

 bling Poplar, Tremble, Populus tremuloides 

 Michx. 



102. Crown of the tree very narrow and spiry. 



