68 WOODY PLANTS 



tinuous. Buds usually solitary, sessile, ovoid, oblique, with about 

 6 spirally arranged scales, striped with faint longitudinal grooves; 

 terminal bud absent. Leaf-scars alternate, crescent-shaped or 

 elliptical, small; bundle-traces 3; stipule-scars unequal. 



1. O. virginiana (Mill. ) K. Koch. Hop Hornbeam . Ironwood. 

 A slender tree up to 20 m. high, the trunk 6 dm. or less in diam- 

 eter, with very hard wood and brownish furrowed bark; twigs 

 pubescent; staminate catkins sessile at ends of twigs of the pre- 

 ceding season; pistillate catkins small, terminal, erect, the flow- 

 ers subtended by a tubular bract which in fruit becomes a closed 

 bladdery bag 12-15 mm. long; ripe pistillate catkins resemble 

 hops, whence the common name. Rich woods. Nova Scotia to Mani- 

 toba and South Dakota, south to Florida and Texas (Fig. 51). 



CARPINUS L. (Betulaceae) 



Deciduous trees with smooth dark bluish-gray bark, the trunk 

 with irregular ridges extending up and down ("muscle-like"). Twigs 

 slender, zigzag, terete; pith small, round or 5-sided, continuous, 

 pale. Buds usually solitary, ovoid, sessile, oblique, with about 

 twelve 4-ranked scales. Leaf-scars alternate, small, crescent- 

 shaped; bundle-traces 3; stipule-scars unequal. 



1. _C_. caroliniana Walt. American Hornbeam . Blue-Beech . 

 Water- Beech. Muscle-Tree. A small tree to 15 m. high, trunk 

 short, often leaning, furrowed and ridged; bark dark bluish-gray, 

 smooth, thin, tight; twigs glabrous or nearly so; wood very hard; 

 buds brown, somewhat silky, less than 5 mm. long; staminate cat- 

 kins entirely enclosed in buds, not visible in winter; fruit subtended 

 by a flat persistent bract which becomes much enlarged (foliaceous) 

 and lobed or incised; nutlet 4 mm. long. Rich woods. New England 

 to Ontario and Minnesota, south to Florida and Texas (Fig. 52). 



BETULA L. (Betulaceae) 



Aromatic deciduous trees or shrubs. Twigs slender, terete; 

 lenticels elongated horizontally (in this respect resembling cherry); 

 pith minute, flattened, continuous, green. Buds moderate, solitary, 

 fusiform-ovoid, sessile, with 2 or 3 visible scales. Leaf-scars 

 alternate, oval, triangular or crescent-shaped; bundle-traces 3. 

 Staminate catkins naked through winter, often 2 or 3 in a cluster; 

 pistillate catkins ovoid or cylindrical. 



a. Twigs with a sweet wintergreen fragrance 



b. Bark on old trunks black; buds sharply 



