50 ELEMENTS OF BOTANY. 



mas 2, bractlets 2, becoming enlarged and enclosing the single 

 bony nut at maturity. 



C. Americana Walt. Hazel-nut. A shrub 4-7 ft. high, 

 young twigs and petioles covered with brownish, viscid hairs ; leaves 

 round-cordate, acute or acuminate, irregularly toothed, nearly smooth 

 above, pubescent below ; involucre longer than the nut and enclos- 

 ing it, glandular-hairy ; nut subglobose, pointed, edible. February- 

 March. On rich soil, borders of meadows and fields. 



IV. BETULA. 



Trees with slender, aromatic twigs and thin, usually straight- 

 veined leaves ; staminate aments drooping, flowers usually 3 

 in the axil of each bract, stamens 4, short, anthers 1-celled ; 

 pistillate aments erect, flowers 2 or 3 in the axil of each bract ; 

 ovary sessile, 2-celled, styles 2 ; bracts 3-lobed ; perianth none; 

 nut broadly winged. 



1. B. NIGRA L. Black Birch. A medium-sized tree with 

 reddish-brown bark ; leaves rhombic-ovate, acute at the apex, acute 

 or obtuse at the base, sharply and doubly serrate, white-downy below, 

 becoming smoother with age, petioles short ; staminate aments 2-3 

 in. long ; pistillate aments l-lg^ in. long, peduncles short, bracts nearly 

 equally 3-cleft, woolly. j\larch- April. River banks. 



2. B. LENTA L. Cherry Birch. Leaves ovate or oblong-ovate, 

 acute, cordate, finely and doubly serrate, silky when young ; petioles 

 about ^ in. long ; staminate aments clustered, 3-4 in. long ; pistillate 

 aments sessile, about 1 in. long, cylindrical bracts spreading, acute, 

 smooth. March- April. River banks, especially in the northern dis- 

 tricts. A large tree with aromatic twigs. The oil contained in the 

 bark and twigs is distilled and used as a substitute for wintersreen. 



V. ALNUS. 



Shrubs or small trees ; leaves petioled, serrate ; flower buds 

 stalked, appearing the previous season ; staminate aments 

 racemed, drooping flowers 3-6 in the axil of each bract, sub- 

 tended by 1-2 bractlets, perianth 4-parted, stamens 4, fila- 

 ments short ; pistillate aments erect, flowers 2-3 in the axil 

 of each bract, perianth replaced by 2-4 minute bractlets which 

 are adherent to the bract ; ovary 2-celled, styles 2, fruit a 



