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 
cc. 
lobe diverging; leaves silvery white beneath; twigs 
rank-smelling when broken...... A. saccharinum, p. 185. 
Leaf-lobes short and broad, the sides of the terminal 
jobe 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 34-1 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 ........... 
re ee eee ee 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 
one one side; medium-sized tree. .A. rubrum, p. 187. 
dd Leaves 4-7 inches broad, thick, pentagonally 5-lobed; 
wings of fruit 114 inches long...................000, 
get ae KE dare aNaiteude SaaS nee A, pseudo-platanus, p. 191. 
