Dicotyledones. 31 



Bark on trunk and old branches pealing off in thin layers. Fruiting aments 

 peduncled. Nut narrower than the wings. In rich woodland and along streams. 



2. Betula occidentalis, Hook. (L., occidentalism western.) WESTERN Red 

 Birch. Trees with smooth brown or greenish brown bark. Leaves from ovate to 

 nearly orbicular, sharply serrate ; smooth on both sides or only slightly pubescent 

 on the veins beneath. Nut narrower than the wings. Fruiting aments peduncled. 



3. Betula nigra, L. (L., w«|.o-e;-, black.) RIVER or Red BIRCH. Slender trees 

 with reddish brown or greenish brown bark which peels in thin layers. Rhombic 

 ovate leaves which are dark green and smooth above, and pale and smooth or 

 somewhat tomentose beneath, Obovate nut broader than the wings. Pistillate 

 aments peduncled. Along streams, etc. 



n. CARPINUS. Hornbeam or Ironwood, 



(The ancient Latin name.) 



Trees or shrubs with snaooth gray bark, and leaves with lateral veins 

 from the midrib nearly parallel and straight. Inflorescence expanding 

 before the leaves. Staminate aments sessile at the ends of short 

 branches ; i staminate flower of 3-12 stamens in the axil of each bract 

 of the ament ; short filaments 2-cleft, each branch bearing an anther 

 sac. Two pistillate flowers in the axil of each bract of, the small termi- 

 nal pistillate aments. Ovary 2-celled ; stigmas 2, sessile, or nearly so. 

 Fruit a small, ovate, nerved nut, subtended by a persistent foliaceous 

 bractlet, 



I. Carpinus Caroliniana, Walt. American Hornbeam or Blue or Water 

 Beech. Small tree with slender gray twigs. Leaves ovate-oblong, acuminate, 

 very sharply doubly serrate, somewhat falcate or inequilateral, green on both sides, 

 and nearly smooth ; bractlet subtending the nutlet 3-lobed and halberd-shaped. 

 Along streams and in moist woods, 



III. dsTRYA. Hop Hornbeam or Ironwood. 



(Greek name for hardwood tree.) 



Slender trees with brownish bark and furrowed trunks. Leaves 

 ovate or oblong-ovate, somewhat inequilateral, slightly pubescent above 

 and beneath, petioles very short. Staminate flowers, of several stamens, 

 occurring singly in the axil of each bract ; filaments forked, each fork 

 bearing an anther sac. Two pistillate flowers in the axil of each bract 

 of the short pistillate ament ; a tubular bractlet surrounding each flower 

 and becoming bladdery in fruit and completely inclosing the small nut- 

 let. Ovary incompletely 2-celled, with 2 ovules ; stigmas 2, long and 

 linear. Border of the adherent calyx short and bearded. 



