104 BETULACEAE 



Famhy I. BETULACEAE Agardh. Birch Family. 



Staminate flowers solitary in the axil of each bract, without a calyx : pistillate 

 flowers with a calyx. 

 Staminate flowers without bractlets : pistillate flowers numerous in spike- 

 like aments : nuts relatively small. 

 Fruit subtended by a flat 3-cleft and incised bractlet. i. Carpinus. 



Fruit enclosed in a membranous bladdery bractlet. 2. Ostrya. 



Staminate flowers with 2 bractlets each: pistillate flowers 2-4 in capitate 

 aments : nuts relatively large. 3. Corylus. 



Staminate flowers 3-6 together in the axil of each bract, with a calyx. 

 Stamens 2 ; filaments 2-cleft, each branch bearing an anther-sac : fruiting 



bracts 3-lobed or entire, deciduous. 4. Betula. 



Stamens 4 : anther-sacs adnate : fruiting bracts woody, erose or toothed, per- 

 sistent 5. Alnus. 



1. CARPINUS L. 



1. Carpinus Caroliniana Walt. Hornbeam. Water Beech. (Man. 

 p. 326 ; I. F.y. rzoy.) In moist woods and along streams, N. S. to Minn., 

 Fla. and Tex. — Pennsylvania : Monroe ; Northampton ; Delaware; 

 Chester ; Lancaster ; Franklin ; Bedford ; Somerset ; Alle- 

 gheny ; Erie. 



2. OSTRYA Scop. 



1. Ostrya Virginioa (Mill.) Willd. Iron-wood. Hop-hornbeam. 

 (Man. p. 327 ; I. F. f. 120S.) In dry woods, Cape Breton Id. to Minn., 

 Fla. and Tex. — Pennsylvania : Pike ; Tioga ; Northampton ; Dela- 

 ware ; Chester ; Lancaster ; Franklin ; Somerset ; Erie, Piesque 

 Isle ; Allegheny. 



3. CORYLUS L. 

 I iivolucral bractlets 2, broad, laciniate. 1. C.Americana. 



Involucral bractlets united, tubular above. 2. C. roslrala. 



1. Corylus Americana Walt. HazEL-nxjT. (Man. p. 327; I. F. /. 

 i2og.') In thickets. Me. and Oat. to Man., Fla. and 'K&-a^.— Penn- 

 sylvania : Pike ; Monroe ; Northampton, College Hill ; Delaware ; 

 Che-ster; Lancaster; Franklin; Huntingdon; Allegheny. 



2. Corylus rostrata Ait. Beaked Hazelnut. (Man. p. 327 ; I. F. 

 /. 1210.) In thickets or woods, N. S. to B. C, Ga., Tenn., Kans. and 



Ore. — Pennsylvania : Pike ; Monroe ; Lackawanna ; Northampton ; 

 Tioga; Bhrks ; Montgomery; Chester; Lancaster; Fulton; 

 Huntingdon ; Somerset. 



4. BETULA L. 



Pistillate and fruiting aments peduncled. 

 Bark of trunk chalky white. 

 Leaf-blades deltoid, acuminate. i. B. populifolia. 



Leaf-blades ovate. 2. B papyri/era. 



Bark reddish or greenish brown. 3. B. nigra. 



Pistillate and fruiting aments sessile at the ends of short branches, 

 a. Bark brown : leaf-blades shining above : mature bracts with 2 short diver- 

 gent lateral lobes : nutwilhtriangular-obovate wings. 4. B.lenta. 



