506 



BETULACEAE. 



Family 6. BETULACEAE Agardh, Aphor. 208. 1825. 



BIRCH FAMILY. 



Monoecious or very rarely dioecious trees or shrubs, with alternate petioled 

 simple leaves, and small flowers in linear-cylindric oblong or subglobose aments. 

 Stipules mostly fugacious. Staminate aments pendulous. Staminate flowers 

 1-3 together in the axil of each bract, consisting of a membranous 2-4-parted 

 calyx or none, and 2-10 stamens inserted on the receptacle, their filaments dis- 

 tinct, their anthers 2-celled, the anther-sacs sometimes distinct and borne on the 

 forks of the 2 -cleft filaments. Pistillate aments erect, spreading or drooping, 

 spike-like or capitate. Pistillate flowers with or without a calyx adnate to the 

 solitary i-2-celled ovary; style 2-cleft or 2-divided; ovules 1-2 in each cavity of 

 the ovary, anatropous, pendulous. Fruit a small compressed or ovoid -globose, 

 mostly i -celled and i -seeded nut or samara. Testa membranous. Endosperm 

 none. Cotyledons fleshy. Radicle short. 



Six genera and about 75 species, mostly natives of the northern hemisphere. 



Staminate flowers solitary in the axil of each bract, destitute of a calyx : pistillate flowers with a calyx. 

 Staminate flowers with no bractlets; pistillate aments spike-like; nut small, subtended by or 



enclosed in a large bractlet. 



Fruiting bractlet flat, 3-cleft and incised, i. Carpinus. 



Fruiting bractlet bladder-like, closed, membranous. 2. Ostrya. 



Staminate flowers with 2 bractlets; pistillate flowers 2-4, capitate; nut large, enclosed by a leafy 



involucre. 3. Corylus. 



Staminate flowers 3-6 together in the axil of each bract, with a calyx ; pistillate flowers without a calyx. 

 Stamens 2; filaments 2-cleft, each fork bearing an anther-sac; fruiting bracts 3-lobed or entire, 



deciduous, 4. Betula. 



Stamens4; anther-sacs adnate ; fruiting bracts wood}', erose or5-toothed, persistent. 5. Alnns. 



i. CARPINUS L. Sp. PI. 998. 1753. 



Trees or shrubs, with smooth gray bark, furrowed and ridged stems and straight-veined 

 leaves, the primary veins terminating in the larger teeth. Aments expanding before the 

 leaves. Staminate aments linear-cylindric, sessile at the ends of short lateral branches of 

 the preceding season, their flowers solitary in the axil of each bract, consisting of 3-12 sta- 

 mens; filaments short, 2-cleft, each fork bearing an anther-sac. Pistillate flowers in small 

 terminal aments, 2 to each bract, consisting of a 2-celled ovary adnate to a calyx and sub- 

 tended by a flat persistent bractlet, which becomes much enlarged, foliaceous and lobed or 

 incised in fruit, the bracts deciduous; style slender or almost none; stigmas 2, subulate. Nut 

 small, ovoid, acute, borne at the base of the large bractlet. [The ancient name.] 



About 12 species, natives of the northern hemisphere, only the folTowing American. 



Carpinus Caroliniana Walt. American Hornbeam. Blue Beech. 



(Fig. 1207.) 



Carpinns Caroliniana Walt. Fl. Car. 236. 



A small tree, with slender terete gray twigs, 

 attaining a maximum height of about 40 and 

 a trunk diameter of 2^. Leaves ovate-ob- 

 long, acute or acuminate at the apex, sharply 

 and doubly serrate all around, rounded or 

 subcordate at the base, somewhat inequilat- 

 eral, 2>^ / -4 / long, I'-i^'wide, green on both 

 sides, glabrous above, slightly pubescent on 

 the veins beneath, petioles very slender, 4"- 

 7 // long; Staminate aments \'-\% r long, their 

 bracts triangular-ovate, acuminate, puberu- 

 lent; anther-sacs villous at the summit; bract- 

 let of the pistillate flowers 3-lobed at the base, 

 firm-membranous, strongly veined and about 

 \' long when mature, its middle lobe lanceo- 

 late, acute, 2-4 times as long as the lateral 

 ones, incised-dentate on one side, often 

 nearly entire on the other; nut somewhat 

 compressed, i" long. 



In moist woods and along streams, Nov.. 

 tia to Ontario and Minnesota, south to Florida 

 and Texas. Wood very hard and strong, durable, light brown ; weight per cubic foot 45 Ibs. April- 

 May, the fruit ripe Aug. -Sept. 



I. 



Water Beech. 



