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 distinct, 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 2-celled ovary; style 2-cleft or 2-divided; ovules 1 or 2 in each cavity of the ovary, anatropous, pendulous. Fruit a small compressed or ovoid-globose, mostly 1-celled and 1-seeded nut or samara. Endosperm none. Cotyledons fleshy.

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 b!actlets; pistillate aments spike-like; nut small, subtended by or enclosed in a large bractlet.

Fruiting bractlet flat, 3-cleft and incised.


Carpitin s.

Fruiting bractlet bladder-like, closed, membranous.



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

leafy involucre.



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

Stamens 2; filaments 2-cleft; fruiting bracts 3-lobed or entire, deciduous.



Stamens 4; anther-sacs adnate; fruiting bracts woody, erose or 5-toothed, persistent


Aln us.

i. CARPINUS (Tourn.) L. Sp. PL 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 stamens; 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 subtended 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, nerved, acute, borne at the base of the large bractlet. [The ancient name.]

About 12 species, only the following American. Type species: Carpinus Betulus L.

I. Carpinus Caroliniana Walt. American Hornbeam. Blue Beech. Water-Beech

Fig. 1490

Carpinus caroliniana Walt. Fl. Car. 236. 1788.

A small tree, with slender terete gray twigs; maximum height about 400, trunk diameter of 2i°. Leaves ovate-oblong, acute or acuminate at the apex, sharply and doubly serrate all around, rounded or subcordate at the base, somewhat inequilateral, 2 1/2'-4' long, i'-1 1/2' wide, green on both sides, glabrous above, slightly pubescent on the veins beneath, petioles very slender, 4"-7" long; staminate aments 1-1 1/2' long, their bracts triangular-ovate, acuminate, puberulent; anther-sacs villous at the summit; bractlet of the pistillate flowers 3-lobed at the base, firm-membranous, strongly 'veined and about 1' long when mature, its middle lobe lanceolate, acute, 2-4 times as long as the lateral ones, incised-dentate on one side, often nearly entire on the outer; nut 2" long.

In moist woods and along streams, Nova Scotia to Ontario and Minnesota, Kansas, Florida and Texas. Wood very hard and strong, durable, light brown; weight per cubic foot 45 lbs. April-May, the fruit ripe Aug.-Sept. Water-beech. Iron-wood.

I Carpinus Caroliniana Walt American Hornbeam Blue 1490