5 o8 BETULACEAE. 



2. Corylus rostrata Ait. Beaked Hazel- 

 nut. (Fig. 1 2 10.) 



Corylus rostrata Ait. Hort. Kew. 3: 364. 1789. 



A shrub, similar to the preceding species, but the 

 foliage usually less pubescent. Leaves ovate or 

 narrowly oval, acuminate at the apex, cordate or 

 obtuse at the base, incised-serrate and serrulate, 

 glabrous, or with some scattered appressed hairs 

 above, sparingly pubescent at least on the veins be- 

 neath, 2 l /'-4' long, i / -2>^ / wide; petioles 2 // -4 // 

 long; involucral bractlets bristly hairy, united to the 

 summit and prolonged into a tubular beak about 

 twice the length of the nut, laciniate at the summit; 

 nut ovoid, scarcely compressed, striate, 5 // -7 // high. 



In thickets, Nova Scotia to British Columbia, south 

 to Georgia, Tennessee, Kansas and Oregon. April- 

 May. Fruit ripe Aug. -Sept. 



4. BETULA L. Sp. PI. 982. 1753. 



Aromatic trees or shrubs, with dentate or serrate leaves, scaly buds and flowers of both 

 kinds in aments expanding before or with the leaves, the pistillate erect or spreading. Stam- 

 inate flowers about 3 together in the axil of each bract, consisting of a membranous, usually 

 4-toothed perianth, 2 stamens, and subtended by 2 bractlets; filaments short, deeply 2-cleft, 

 each fork bearing an anther-sac. Pistillate flowers 2 or 3 (rarely i) in the axil of each bract, 

 the bracts 3-lobed, or sometimes entire, deciduous with the fruits; perianth none; ovary ses- 

 sile, 2-celled; styles 2, stigmatic at the apex, mostly persistent. Nut small, compressed, 

 membranous-winged on each side (a samara), shorter than the bracts. [The ancient name.] 



About 35 species, natives of the north temperate and arctic zones. 



# Trees. 

 Fruiting aments peduncled; bark chalky -white. 



Leaves deltoid, acuminate; lateral lobes of fruiting bracts short, divergent, i. B. populifolia. 



Leaves ovate or suborbicular; lateral lobes of the fruiting bracts ascending. 2. B. papyrifera. 

 Fruiting aments peduncled; bark greenish -brown or brown. 



Western; leaves ovate, often obtuse at the base. 3. B. occidentalis. 



Eastern; leaves rhombic, acute at both ends. 4. B. nigra. 



Fruiting aments sessile, at the ends of short branches; bark brown or yellowish. 



Fruiting bracts 2" long, lobed at the apex; leaves shining above. 5. B. lenfa. 



Fruiting bracts 4" long, lobed to about the middle; leaves dull above. 6. B. lutea. 



* * Shrubs. 



Twigs glandular- warty; leaves glabrous. 7. B. glandulosa. 



Twigs not glandular-warty, glabrous or pubescent. 



Leaves glabrous; upper fruiting bracts mostly entire. 8. B. nana. 



Young foliage densely pubescent; bracts 3-lobed. 9. B. pumila. 



i. Betula populifolia Marsh. American White Birch. (Fig. 1211.) 



Bet ula populifolia Marsh. Arb. Am. 19. 1785. 



B. alba var. populifolia Spach, Ann. Sci. Nat. (II. i 15: 



187. 1841. 



A slender tree with very white smooth bark, 

 tardily separating in thin sheets; maximum height 

 45; trunk diameter i>; the twigs russet, warty. 

 Leaves deltoid, pubescent on the veins when 

 young, nearly glabrous when old, minutely glandu- 

 lar, dark green above, light green beneath, long- 

 acuminate, sharply dentate and commonly some- 

 what lobed, obtuse or truncate at the base, 

 2^' long, i / -2 / wide, slender-petioled ; petioles 

 channeled; staminate aments 2'-$' long; pistillate 

 ameuts cylindric, in fruit 9 // -i8 // long, 3 // -5 // in 

 diameter, slender-peduncled; fruiting bracts pu- 

 berulent, i // -2 // long, their lateral lobes divergent, 

 larger than the middle one; nut narrower than its 

 wings. 



In moist or dry soil, New Brunswick to southern On- 

 tario, Pennsylvania and Delaware. Wood soft, weak, 

 light brown; weight per cubic foot 36 Ibs. Leaves tremulous like those of the Aspens. May. 



