i. Leaves very glabrous both sides; fruit a prickly bur.                   j. Leaves 3-5 inches long, very lustrous beneath; bark close, smooth, steel-gray. FAGUS, p. 93. jj. Leaves 6-8 inches long, not lustrous beneath; bark fissured, brownish. CASTANEA, p. 95. ii. Leaves pubescent or white-tomentose, at least beneath; fruit not a prickly bur. j. Leaves 2-4 inches long, broadly ovate to suborbicular; fruit a very small capsule, falling in spring. POPULUS, p. 44. jj. Leaves 4-7 inches long, oblong-lanceolate to obovate; fruit an acorn, falling in autumn. QUERCUS, p. 96. hh. Teeth fine, 6-many per inch of margin. i. Leaf-petioles laterally compressed; leaves tremulous. POPULUS, p. 44. ii. Leaf-petioles terete; leaves not tremulous. j. Leaf-blades at least 3 times as long as they are broad.                     k. Twigs brittle; fruit a very small capsule, falling in spring. SALIX, p. 34. kk. Twigs tough; fruit a fleshy drupe, falling in late summer or autumn. PRUNUS, p. 152. jj. Leaf-blades not more than twice as long as they are broad. k. Leaf-blades about twice as long as they are broad.                       l. Margin of leaves singly serrate; fruit fleshy.                         m. Lenticels conspicuous; pith whitish or brownish; bark easily peeled off in papery layers; buds ovoid. PRUNUS, p. 152. mm. Lenticels inconspicuous; pith greenish; bark not separable into papery layers; buds narrow-conical. AMELANCHIER, p. 149. ll. Margin of leaves doubly serrate; fruit not fleshy. m. Trunk fluted; fruit inclosed within a halberd-shaped involucre. CARPINUS, p. 83. 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. l. Lower side of leaves more or less downy; sap milky; leaves not crowded on short, spur-like branchlets; fruit berry-like, black. MORUS, p. 135. ll. Lower side of leaves glabrous; sap not milky; leaves crowded on short, spur-like branchlets; fruit a large, green