1-2 teeth per centimeter of margin --46.
40a. Petioles laterally compressed 2a, in =SALICACEAE=, p. 19.
40b. Petioles not compressed --41.
41a. Leaves, or many of them, crowded on short spur-like branches --42.
41b. Leaves scattered, not on short spur-like branches --43.
42a. Bark of the trunks separating in thin papery or leathery sheets =BETULACEAE=, p. 21.
42b. Bark of the trunk not papery or leathery 24b, in =ROSACEAE=, p. 53.
43a. Lateral leaf-veins straight and parallel, and terminating in the teeth =BETULACEAE=, p. 21.
43b. Lateral veins more or less curved, and not ending in the teeth --44.
44a. Leaves palmately veined, about as broad as long; juice somewhat milky 2b, in =URTICACEAE=, p. 23.
44b. Leaves pinnately veined; juice not milky --45.
45a. Willows, with slender leaves and brittle twigs 8a, in =SALICACEAE=, p. 19.
45b. Trees with lanceolate, ovate, or oblong leaves and tough twigs 30, in =ROSACEAE=, p. 54.