SUMMER KEY TO THE SPECIES OF ACER 



a. Leaves simple ; twigs usually without whitish bloom, 

 b. Leaf-sinuses acute at the base. 



c. Leaf-lobes long and narrow, the sides of the terminal 

 lobe diverging; leaves silvery white beneath; twigs 



rank-smelling when broken A. saccharinum, p. 185. 



cc. Leaf-lobes short and broad, the sides of the terminal 

 lobe converging; leaves not conspicuously white be- 

 neath; twigs not rank-smelling when broken. 



d. Leaves 2-4 inches broad, thin, not pentagonally 5- 

 lobed; wings of fruit Y\-\ inch long. 



e. Leaves distinctly white-downy beneath; twigs ap- 

 pressed-hairy, at least near the tip; fruit hanging in 

 pendulous racemes, persistent on the tree until 

 autumn ; seed portion with pit-like depression on 



one side ; usually a shrub or bushy tree 



A. spicatum, p. 179. 



ee. Leaves glabrous or nearly so beneath; twigs glab- 

 rous; fruit hanging in clusters, falling in early 

 summer; seed portion without pit-like depression 

 on one side; medium-sized tree. .A. rubrum, p. 187. 

 dd. Leaves 4-7 inches broad, thick, pentagonally 5-lobed; 



wings of fruit i l /2 inches long 



A. psendo-platanus, p. 191. 



172 



