e. Leaves heart-shaped or rounded; fruit a legume 



CERCIS, p. 167. 



ee. Leaves oval, ovate or obovate ; fruit not a legume, 

 f. Branches armed with stout, straight spines; fruit 



large, orange-like MACLURA, p. 133. 



ff. Branches without spines; fruit small, not orange- 

 like. 



g. Fruit an acorn j QUERCUS, p. 96. 



gg. Pruit a drupe or berry. 



h. Twigs spicy-aromatic when bruised ; leaves of 



many shapes on the same branch 



SASSAFRAS, p. 139. 



hh. Twigs not spicy-aromatic ; leaves not of many 



shapes on the same branch. 

 i. Leaves thick, abruptly pointed, very lustrous 

 above, not clustered at the ends of the 



branches NYSSA, p. 209. 



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^-2 times as long as they are 

 broad, oval to ovate, 

 i. Leaves thin, coarsely but singly serrate ; 



fruit a globular drupe, ripe in autumn 



CELTI'S, p. 131. 



ii. Leaves thick, coarsely and doubly serrate; 



fruit a samara, ripe in spring 



ULMUS, p. 122. 



gg. Base of leaves essentially symmetrical, 

 h. Teeth coarse, 2-5 per inch of margin, 

 i. Leaves very glabrous both sides; fruit a 

 prickly bur. 



xxn 



