FLORA OF THE DISTRICT OF COLUMBIA. 137 



2. OSTRYA Scop. 



1. Ostrya virginiana (Mill.) Willd. Hop hornbeam. Ironwood. 



Woods; Potomac valley. Apr.; fr. July. Eastern N. Amer. 



3. CORYLTJS L. 



1. Corylus americana Walt. Hazelnut. 



LoAv places. March; fr. Aug. Eastern U. S. 



4. ALNUS Hill. 



1. Alnus rugosa (DuRoi) Spreng. Alder. 



Swamps and low ground. March. Eastern U. S. (A. serrulata Willd.) 



6. BETULA L. Birch. 



Leaves rhombic-ovate; bark yellow; twigs grayish, pubescent 1. B. nigra. 



Leaves ovate-oblong, cordate; bark brown; twigs glabrous or nearly so 2. B. lenta. 



1. Betula nigra L. Black, red, or river birch. 

 Along streams and in low wet places. Apr.; fr. May. Eastern U. S. 



2. Betula lenta L. Cherry or sweet birch. 

 Bluffs along the Potomac above Cabin John. Apr.; fr. May. Eastern U. S. " 



38. FAGACEAE. Beecli Family. 



Leaves not straight- veined , entire, crenate, lobed, or pinnatifid; fruit an acorn 

 (1-seeded nut) partially inclosed in a cuplike involucre. Staminate flowers in 

 slender pendulous aments; pistillate flowers borne singly or in clusters. 



3. QUERCUS. 



Leaves straight- veined, uniformly serrate, oblong-lanceolate to ovate-oblong or 



oblanceolate; fruit not an acorn. 



Leaves ovate-oblong; staminate flowers in globose long-stalked heads; fruit (bur) 



ovate, 1.5 cm. long or less, the involucre prickly, splitting into 4 valves; nut 



2, 3-angled; trees with smooth, light gray bark 1. FAGUS. 



Leaves oblong-lanceolate to oblanceolate; staminate flowers in long slender aments, 

 in separate clusters or in the upper part of the pistillate aments; fruit (bur) 

 globular, 2.5-7 cm. in diameter; nuts 2 or 3 or more, inclosed in a densely 

 prickly involucre; trees or shrubs 2. CASTANEA. 



1. FAGUS L. 



1. Fagus grandifolia Ehrh. " Beech. 



Deciduous woods. Apr.-May; fr. Sept.-Oct. Eastern N. Amer. (F. ferruginea 

 Ait.) 



2. CASTANEA Hill. 



Plants trees; leaA^es 10-20 cm. long or more, oblong-lanceolate, glabrous at maturity. 



Bur about 7 cm. in diameter 1. C. dentata. 



Plants shrubs; leaves densely white-pubescent or tomentulose beneath, oblong- 

 lanceolate or oblanceolate. 



Leaves about 10 cm. long; bur 2.5 cm. long or smaller 2. C. pumila. 



Leaves 10-20 cm. long or more; mature fruit unknown 3, C. neglecta. 



1. Castanea dentata (Marsh.) Borkh. Chestnut. 

 Deciduous woods. June; fr. Sept.-Oct. Eastern U. S. (C vulgaris americana 



A. DC) 



2. Castanea pumila (L.) Mill. Chinquapin. 

 Deciduous and coniferous woods. June; fr. Sept.-Oct. Southern states, north 



to Pa. 



