A family of 4 to 6 genera and about 140 species, mostly in the Northern 

 Hemisphere. Sometimes divided so that Carpinus and Ostrya constitute a separate 

 family, the Carpinaceae. 



1. Staminate flowers solitary in the axil of each bract, without a calyx or 

 bracteoles; pistillate flowers with a calyx or bracteoles; bracts of 

 the pistillate ament deciduous; nutlets wingless, more or less en- 

 veloped by an involucre formed by the enlargement of the bract 

 and bractlets of the flower 1. Carpinus 



1. Staminate flowers 2 or more in the axil of each bract, with a calyx or 



bracteoles; pistillate flowers without a calyx or bracteoles; bracts 

 of the pistillate ament persistent or eventually deciduous; nutlets 

 winged or with a coriaceous margin, without an involucre, borne 

 in an ovoid to oblong-ellipsoid strobile (2) 



2(1). Pistillate aments solitary; fruiting aments not persistent, the bracts thin, 

 3-lobed, deciduous with or soon after the nutlet; stamens 2, bifid; 

 buds not stalked; trees with usually exfoliating bark 2. Betula 



2. Pistillate aments racemose; fruiting aments persistent, the bracts thick and 



semi-woody, not deeply lobed, persistent; stamens 4, not bifid; buds 

 stalked; shrubs with smooth or somewhat scaly bark 3. Alnus 



1. Carpinus L. Hornbeam. Ironwood 



An Old World genus of about 35 species, with one in America. 



1. Carpinus caroliniana Walt. American hornbeam, blue-beech, lechillo. 



Small tree to 10 m. tall, with somewhat flattened and twisted trunk and smooth 

 grayish bark; leaves oblong to narrowly oblong-ovate or elliptic-lanceolate, 

 rounded at base, subobtuse to acuminate at apex, to 9 cm. long and 45 mm. wide, 

 more or less doubly serrate; staminate aments pendulous, the ovate scales each 

 subtending a solitary naked flower that is composed of several divided filaments 

 each bearing 2 apically pilose half-anthers; fruiting aments ovoid to short- 

 cylindric, to 5 cm. long; bracts about 2 cm. long, ovate, subtending 2 flowers, 

 chartaceous, halberd-shaped, with 1 or 2 divergent basal lobes, entire or with 

 a few blunt teeth along one side of the midlobe; nutlet ovoid, several-nerved. 



Rich woods and bottomlands along streams subject to flooding, in e. Okla. 

 (Waterfall) and e. Tex., Mar.-May; from Fla. and Tex., n. to Md., Tenn. and s. 

 111. 



2. Betula L. Birch 



Trees or rarely shrubs with the outer bark often separable in sheets, the 

 branchlets dotted; buds sessile, scaly; staminate aments terminal and lateral, 

 sessile, formed in summer, remaining naked during winter to expand in early 

 spring with or preceding the leaves; flowers 3 (the bractlets 2) to each peltate 

 scale or bract of the aments, consisting each of a calyx of 1 scale bearing 4 short 

 filaments with 1 -celled anthers or strictly of 2 bipartite filaments with each 

 division bearing an anther-cell; pistillate aments (strobiles) ovoid to cylindrical, 

 usually terminating very short 2-leaved early lateral branches of the season 

 (spurs); flowers 2 or 3 to each 3-lobed bract, without bractlets or calyx, each 

 with a naked ovary, becoming a winged and scalelike nutlet or small samara 

 crowned by the two spreading stigmas. 



About 60 species that are widely scattered in the Northern Hemisphere. 



1. Bark readily exfoliating; bracts of pistillate aments subequally lobed, cuneate- 



tapered to base; distribution in eastern Oklahoma and Texas 



1. B. nigra. 



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