ii. Leaves thin, long-pointed, not lustrous above, clustered

at the ends of the branches. CORNUS, p. 202.

dd. Margin of leaves serrate, toothed or lobed.

e. Margin of leaves serrate to toothed.

f. Branches armed with stiff, sharp thorns. CRATAEGUS, p. 151.

ff. Branches not armed.

g. Base of leaves decidedly oblique.

h. Leaf-blades about as long as they are broad, heart-shaped. TILIA, p. 201.

hh. Leaf-blades 1-1/2 - 2 times as long as they are broad, oval to ovate.