A. Leaves narrow, willow-like; Southern tree.
Willow Oak.
AA. Leaves oval, with deeply-cleft margins.
B. Acorn cups, shallow, broader than high.
C. Tree pyramidal, twigs with pin-like spurs.
Pin Oak.
CC. Tree spreading; acorns large, in shallow saucers.
Red Oak.
BB. Acorn cups as deep as broad.
C. Leaves thin, smooth, deeply cut; acorn cup drawn in at the top.
Scarlet Oak.
CC. Leaves leathery, rough, with rusty hairs beneath; acorn cup
not drawn in at the top.
Black Oak.