A. Leaves simple.
B. Bloom before the leaves open; seeds ripe in May.
C. Flowers red; leaves pale beneath, with three triangular lobes.
Red Maple.
CC. Flowers greenish; leaves pale beneath, deeply cleft, with
long, spiny lobes.
Silver Maple.
BB. Bloom after the leaves open; seeds ripe in autumn.
C. Leaves wider than long; lobes spiny-tipped.
D. Lining of leaves, pale; keys joined at acute angle.
Sugar Maple.
DD. Lining of leaves, not pale; keys joined at wide angle.
Norway Maple.
CC. Leaves circular, lobed; tree prostrate.
Vine Maple.
CCC. Leaves about as wide as long; trees small.
D. Bark striped with white lines; flowers and seeds in
dense, pendant clusters.
Striped Maple.
DD. Bark not striped; flowers and seeds in pendant clusters.
Mountain Maple.
AA. Leaves compound, of 3 to 7 leaflets.
Ash-leaved Maple. Box Elder.