ll. Bundle-scars not depressed, inconspicuous; bark thin,

broken into narrow, flattish strips, loose at the ends. OSTRYA, p. 81.

ii. Stipule-scars absent.

j. Buds silky-pubescent, depressed; twigs stout, clumsy, blunt, with conspicuous leaf-scars. GYMNOCLADUS, p. 163.

jj. Buds glabrous, not depressed; twigs slender, with inconspicuous leaf-scars.

k. Buds 1/8 inch long, obtuse, somewhat flattened and appressed; pith with reddish longitudinal streaks. CERCIS, p. 167.

kk. Buds 1/8-1/4 inch long, acute, not flattened nor appressed; pith without reddish streaks. PRUNUS, p. 153.

ff. Bundle-scars 4-many.

g. Bundle-scars in a single U-shaped line.

h. Terminal bud present; fruit berry-like; a shrub or small tree. PYRUS, p. 143.

hh. Terminal bud absent; fruit not berry-like; large trees.

i. Stipule-scars present; twigs slender.

j. Stipule-scars encircling the twig; leaf-scars nearly surrounding the bud; bark peeling off in thin plates, exposing the lighter colored inner bark. PLATANUS, p. 141.

jj. Stipule-scars not encircling the twig; leaf-scars not nearly surrounding the bud; bark thick, rough-ridged, not exposing the inner bark. ULMUS, p. 123.

ii. Stipule-scars absent; twigs very stout.

j. Bundle-scars usually not more than 5. GYMNOCLADUS, p. 163.

jj. Bundle-scars usually 6-12. AILANTHUS, p. 171.

gg. Bundle-scars variously grouped or scattered, but not in a single line.

h. Terminal bud present.

i. Stipule-scars present.

j. Stipule-scars encircling the twig; visible bud-scales 2, united. LIRIODENDRON, p. 137.

jj. Stipule-scars not encircling the twig; visible bud-scales more than 2, not united.

k. Buds 4 times as long as broad, not clustered at the tips of vigorous shoots; fruit a prickly bur. FAGUS, p. 93.

kk. Buds not 4 times as long as broad, usually clustered at the tips of vigorous shoots; fruit an acorn. QUERCUS, p. 98.

ii. Stipule-scars absent. CARYA, p. 67.

h. Terminal bud absent (occasionally present in _Castanea_).