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-lob- 

 ed; wings of fruit M-I 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 not distinctly white-downy beneath; twigs 



glabrous; 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-lohcd ; 



wings of fruit l l /z inches long 



A. pseudo-platanus, p. 191. 



172 



