62 BETULACEAE. 



OSTRYA. Hop Hornbeam. 



Deciduous small trees with scaly bark : somewhat reddish hard 

 wood with minute diffused ducts and fine medullary rays; slender 

 somewhat zig-zag terete twigs ; roundish homogeneous pale pith ; 

 alternate 2-ranked somewhat raised small crescent-shaped leaf 

 scars with 3 bundle-traces ; narrow stipule-scars ; elongated ovoid 

 moderate solitary sessile buds with several spirally placed finely 

 ridged scales, the end bud lacking; simple serrate petioled mod- 

 erate leaves ; inconspicuous monoecious apetalous flowers in small 

 catkins ; and small seed-like fruits, each subtended by a larger thin 

 scale, aggregated in a hop-like cluster. 

 Twigs from villous and glandular, glabrescent. Q. virina::a. 



CARPINUS. Hornbeam. Blue Beech. 



Deciduous small trees with fluted trunks; smooth gray bark; 

 pale hard wood with minute diffused ducts and extremely fine 

 medullary rays ; slender zig-zag terete twigs ; rather round homo- 

 geneous pale pith ; alternate 2-ranked low, small crescent-shaped 

 leaf-scars with 3 bundle-traces; narrow stipule-scars; elongated- 

 ovoid rather small solitary sessile buds with several spirally 

 placed smooth scales, the end bud lacking ; simple doubly ser- 

 rate peiioled moderate leaves ; inconspicuous monoecious apetal- 

 ous flowers in small catkins ; and small ribbed seed-like fruits, 

 each subtended by a hastate bract. 



1. Buds small (3 mm.), dark, for a time hairy. C. caroliniana. 

 Buds large (5 mm.), light brown, glabrous. 2. 



2. Tree round-topped. 3. 



Tree conical. C. Betulus pyramidalis. 



3. Leaves green. 4. 



Leaves for a time purple. C. Betulus purpurea. 



4. Leaves merely toothed. C. Betulus. 

 Leaves cut or lobed. C. Betulus incisa. 



BETULA. Birch. 



Deciduous trees or occasionally shrubs often with papery- 

 flaking or white bark with transversely elongated lenticels ; pale 

 or reddish often hard wood with minute diffused ducts and very 



