KEY TO GENERA 27 



180. Bud-scales 2. . . Tilia , p. 151 



180. Bud-scales several. 181 



181. Buds nearly globose, with 4-6 scales. . . Corylus, p. 67 



181. Buds oblong, with about 12 scales. . . Carpinus , p. 68 



182. Exposed bud-scales 2. . ,Cornus,p. 158 



182. Exposed bud-scales more than 2, or the buds naked. 183 



183. Without stipules or stipule -scars. 184 



183. With stipules or stipule-scars. 186 



184. Aromatic; twigs green. . . Sassafras, p. 98 



184. Not aromatic. 185 



185. Buds woolly or gummy. . . Sorbus, p. 109 



185. Buds not woolly or gummy. . . Pyrularia, p. 89 



186. Stipule-bases present, or stipule-scars short. 187 



186. Stipule-scars elongated. . . Betula, p. 68 



187. Stipule-scars or bases on a leaf-cushion. 188 



187. Stipule-scars not on a leaf-cushion. 189 



188. Inner bark with a disagreeable odor; lenticels 

 horizontally elongated. . . Prunus, p. 121 



188. Inner bark not with a disagreeable odor; lenticels prominent, 

 not horizontally elongated, . . Rhamnus , p. 143 



189. Bundle-traces confluent, or twigs hairy. . .Rhamnus, p. 143 



189. Bundle-traces separate, or twigs glabrous. 190 



190. Lenticels horizontally elongated. . . Prunus , p. 121 



190. Lenticels not horizontally elongated. . . Crataegus , p. 112 



191. Stipule-scars nearly or quite encircling the twig. 192 



191. Not as above. 195 



192. Buds long and pointed. 193 



192. Buds not as above. 194 



193. Leaf-scars small. . . Fagus, p. 73 



193. Leaf-scars large. . . Magnolia , p. 94 



194. Buds large, flattened. . . Liriodendron, p. 95 



194. Buds short, ovoid. . . Ulmus, p. 83 



195, Bundle-traces many, mostly in 3 groups; leaf-scars lobed. 196 



195. Not as above. 197 



196. Pith chambered. . . Juglans, p. 61 

 196. Pith continuous. . . Carya, p. 61 



