Rhamnus sp. 2, 3 (p. 724, 725). _cc_ Winter-buds with a single pair of connate scales. Primary veins arching and uniting within the margins; leaves simply serrate or crenate, sometimes entire. Salix (p. 138). Primary veins extending to the teeth, leaves doubly serrate, often slightly lobed. Alnus (p. 220). _ccc_ Winter-buds with several pairs of imbricate scales. _d_ Terminal buds wanting; branchlets prolonged by an upper axillary bud. Juice milky; leaves usually ovate, often lobed. Morus (p. 328). Juice watery; leaves not lobed. Leaves distinctly oblique at base. Leaves with numerous prominent lateral veins. Leaves generally broad-ovate, simply serrate, stellate-pubescent at least while young, rarely glabrous. Tilia (p. 732). Leaves never broad-ovate, usually doubly serrate, more or less pubescent with simple hairs, at least while young. Winter-buds ovoid, usually acute, ⅓ to nearly as long as petioles; leaves 1′—7′ long, doubly serrate. Ulmus (p. 309). Winter-buds subglobose, minute; leaves 2′—2½′ long, crenate-serrate. Planera (p. 316). Leaves 3 or 4-nerved from the base. Celtis (p. 318). Leaves slightly or not at all oblique at base. Leaves 3-nerved from the base, glandular-crenate or glandular-serrate. Ceanothus (p. 726). Leaves not or obscurely 3-nerved at base, usually doubly serrate. Leaves blue-green; petioles ¼′—½′ long; bark smooth, gray-brown. Carpinus (p. 201). Leaves yellow-green. Bark rough, furrowed; petioles ⅛′—¼′ long; leaves not resinous-glandular. Ostrya (p. 202). Bark flaky or cherry-tree like; petioles ¼′—1′ long; leaves often resinous-glandular while young. Betula (p. 205). _dd_ Terminal buds present. Primary veins arching and uniting within the margin