104 BETULACEAE 



Family i. BETULACEAE Agardh. Birch Family. 



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

 flowers with a calyx. 

 Staminate flowers without bracllets : pistillate flowers numerous in spike- 

 like aments : nuts relatively small. 

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



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



Staminate flowers with 2 bracllets 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. Carpiaus Caroliiiiana Walt. Hornbeam. Water Beech. (Man. 

 p. 326 ; I. F. f. I20J. ) In moist woods and along streams, N. S. to Minn., 

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

 Chester ; Lancaster ; Franklin ; Bedford ; Somerset ; AllB- 

 OHENY ; Erie. 



2. OSTRYA Scop. 



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

 (Man. p. 327; I. V. 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. 

 Iiivolucral bractlets 2, broad, laciniate. i. C. Americana. 



I nvolucral bractlets united, tubular above. 2. C. roslrala. 



1. Corylus Americana Walt. Hazel-nuT. (Man. p. 327; I. F. /. 

 7^09.) Ill thickets, Me. and Out. to Man., Fla. and Kans. — Penn- 

 sylvania: Tike; Monroe; Northampton, College Hill ; 1'elaware; 

 Chester; Lancaster; Franklin; Huntingdon; Allegheny. 



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

 f. I2TO.) In thickets or woods, N. S. to B. C, Ga., Tenn., Kans. and 

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

 TioG.\ ; Bkrks ; 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. popitli folia. 



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 : nut with triangular-obovate wings. 4. B. lenta. 



