Michigan Trees: A Handbook of the Native and Most Important Introduced Species
mm. Trunk not fluted; fruit not inclosed within a
halberd-shaped involucre.
n. Bark of trunk gray-brown, broken into narrow, flattish pieces loose at the ends; fruit in hop-like strobiles. OSTRYA, p. 81.
nn. Bark of trunk white, yellow or dark brown, platy or cleaving off in papery layers; fruit not in hop-like strobiles. BETULA, p. 84.
kk. Leaf-blades almost as broad as they are long.