24 BETULACEAE 



absent; rather large broad but pinnately veined stalked simple 

 leaves; inconspicuous monoecious apetalous flowers in catkins; 

 and light brown hard-shelled rather small nuts in green or 

 membranaceous husks. 



1. Husk ot 2 nearly or quite separate bracts. 2. 

 Husk tubular. 8. 



2. Husk bur-like. C. ferox. 

 Husk unarmed. 3. 



3. Husk parted into linear divisions. C. colurna. 

 Husks with broader divisions. 4. 



4. Husk open, hardly longer than the short nut. 5. 



Husk closely applied to and surpassing nut. C. americana. 



5. Leaves laciniate. C. Avellana laciniata. 

 Leaves not deeply parted. 6. 



6. Rather upright. 7. 



Branches drooping. C. Avellana pendula. 



7. Leaves green. (European hazel). C. Avellana. 

 Leaves yellow. C. Avellana aurea. 

 Leaves purple. C. Avellana atropurpurea. 



8. Husk merely pubescent; nut elongated. 9. 



Husk bristly. (Beaked hazel). C. rostrata. 



9. Leaves green. (Filbert). C. maxima. 

 Leaves purple. C. maxima pupurea. 



OSTBYA. 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 homo- 

 geneous pale pith; alternate 2-ranked somewhat raised small 

 crescent-sihaped leaf scars with 3 bundle traces; narrow stip- 

 ule-scars; elongated ovoid moderate solitary sessile buds with 

 several spirally placed finely ridged scales, the end bud lack- 

 ing; simple serrate petioled moderate leaves; inconspicuous 

 monoecious apetalous flowers in small catkins; and small 

 seed-like fruits, each subtended by a larger thin scale, ag- 

 gregated in a hop-like cluster. 

 Twigs villous 1 and glandular or glabrescent. O. virginiana. 



