18 Bulletin 194 



m. Lenticels conspicuous ; pith whitish or 

 brownish ; bark easily peeled off in 

 papery layers; buds ovoid, 



Prunus, p. 149. 

 iiiiii. Lenticels inconspicuous ; pith greenish : 

 bark not separable into papery layers ; 

 buds narrow-conical, 



Amelanchier, p. 145. 

 //. Margin of leaves doubly serrate ; fruit not 

 fleshy. 



m. Trunk fluted ; fruit inclosed within a 

 halberd-shaped involucre, ' 



Carpinus, p. 95. 

 mm. Trunk not fluted ; fruit not inclosed 

 within a halberd-shaped involucre. 

 n. Bark of trunk gray-brown, broken 

 into narrow, flattish pieces loose at 

 the ends ; fruit in hop-like strobiles, 

 Ostrya, p. 93. 

 nn. Bark of trunk white, yellow or dark 

 brown, platy or cleaving off in papery 

 layers ; fruit not in hop-like strob- 

 iles Betula, p. 97. 



kk. Leaf-blades almost as broad as they are 

 long. 



/. Lower side of leaves more or less downy ; 

 sap milky ; leaves not crowded on short, 

 spur-like branchlets ; fruit berry-like, 



black Moms, p. 137. 



//. Lower side of leaves glabrous ; sap not 

 milky ; leaves crowded on short, spur-like 

 ■ branchlets ; fruit a large, green pome, 



Pyrus, p. 143. 

 ec. Margin of leaves distinctly lobed. 



/. Fruit an acorn Quercus, p. 1 12. 



ff. Fruit not an acorn. 



g. Leaf-lobes entire ; leaves lustrous above, their 

 petioles 5-6 inches long Liriodendron, p. 139. 



