346 FAGACEAE 
2. Betula lénta L. A forest tree reaching a maximum height of 25 m. and a trunk 
diameter of 1.5 m. Trunk clothed with a brown exfoliating aromatic bark: leaves aro- 
matic ; blades ovate, oblong-ovate or oblong-lanceolate, 4-12 cm. long, acute or acuminate, 
finely doubly serrate, rounded or cordate at the base, dark-green and shining above, paler 
and silky on the nerves beneath; petioles 0.5-2 cm. long, sometimes pubescent: staminate 
aments 5-10 em. long; bracts ovate, about 2.5 em. long, naked like the suborbicular bractlets: 
pistillate aments about 1.5 cm. long, accrescent into cones 2-3 em. long, whose bracts are 
hastate or the lateral lobes ascending, glabrous or pubescent : nuts oval or obovoid, about 3 
mm. long, each furnished with a triangular-obovate wing. 
In woods, Newfoundland to Minnesota, Tennessee and Florida. SWEET, CHERRY OR BLACK BIRCH. 
3. Betula lütea Michx. f. A forest tree, reaching a maximum height of about 30 m. 
and a maximum trunk diameter of 2m. Trunk clothed with a yellowish or silvery slightly 
bitter and aromatic bark, which is close or separated in thin layers : leaves barely aromatic ; 
blades ovate or oblong-ovate, 5-10 cm. long, usually acuminate at the apex, sharply and 
doubly serrate, rounded or cordate at the base, dull green and glabrous above, pubescent on 
the nerves beneath ; petioles 0.5-1.5 cm. long: staminate aments 5-10 cm. long; bracts 
ovate or ovate-oval, about 2.5 mm. long, obtuse, ciliate and colored at the apex like the 
reniform bractlets : pistillate aments about 1.5 cm. long, accrescent into cones 2-4 cm. long, 
their bracts 3-lobed, ciliate, ascending: nuts elliptic, 4 mm. long, rather pointed at both 
ends, each furnished with an orbicular-obovate wing. 
h In woods, Newfoundland to Manitoba and the mountains of Georgia. GRAY BIRCH. YELLOW 
IRCH. 
2. ALNUS L. 
Shrubs or trees, with a pale astringent bark, and terete branchlets. Staminate flowers 
in drooping aments. Calyx usually 4-lobed orirregularly 10-12-lobed. Stamens as many as 
the calyx-lobes and opposite them, or rarely half their number : anthers introrse. Pistillate 
flowers in ovoid or oblong, cone-like aments : bracts bearing 2 flowers, which are subtended 
by 2-4 minute bractlets, becoming woody and truncate or lobed at the apex, persistent. 
Ovary 2-celled, naked. Nut minute, flattened, winged or wingless, the outer coat thin-mem- 
branous, the inner thick-crustaceous. Seed solitary, filling the cavity of the nut. 
Peduncles shorter than the mature fertile aments: nuts merely margined. 1. A. rugosa. 
Peduncles as long as the mature fertile aments or longer: nuts broadly winged. 2. A. Alnobetula. 
1. Alnus rugósa (Du Roi) K. Koch. A shrub or small tree reaching a height of 
about 13 m. and a trunk diameter of 15 em. Stems clothed with a pale smooth bark, the 
twigs pubescent and slightly glutinous : leaf-blades thickish, obovate or oval, 4-10 cm. long, 
obtuse or rarely acute atthe apex, undulately toothed and irregularly serrulate, rounded or 
acutish at the base, glabrous on both surfaces, or either pubescent on the nerves beneath or 
the whole lower surface tomentose ; petioles 0.5-15 mm. long: staminate aments drooping, 
8-12 cm. long, appearing before the leaves ; bracts orbicular-ovate, short acuminate, nearly 
1.5 mm. long, the bractlets suborbicular : pistillate aments very small, developing into oval 
or oblong cones 1.5-2 cm. long, their bracts flabellate, cuneate at the base, shallowly 3- 
lobed: nuts suborbicular or rather ovoid, 1.5 mm. long, flattened, furnished with sharp 
margins. [A. serrulata Willd.] 
On banks of streams, in swamps and on hillsides, Maine to Minnesota, Floridaand Texas. Winter 
and spring. SMOOTH ALDER. 
2. Alnus Alnobétula ( Ehrh.) K. Koch. A shrub ranging from less than 1 m. to 3 
m. in height. Stems often diffusely branched, the twigs and young foliage glutinous and 
usually pubescent: leaf-blades oval or ovate, 3-9 cm. long, rounded or acute at the apex, 
unevenly serrulate and sometimes incised-toothed, obtuse or cordate at the base, glabrous 
and dark green above, glutinous and more or less pubescent, especially on the nerves 
beneath ; petioles 5-25 mm. long: staminate aments 5-10 em. long, rather slender, usually 
appearing with the leaves: pistillate aments developing ovoid or oblong, long-peduncled 
cones, 1-2 em. long, their bracts flabellate, undulately-lobed at the top: nuts oblong or 
obovoid, 2 mm. long, furnished with orbicular-obcordate wings.  [ A. viridis (Chaix. ) DC.] 
In stony soil, Arctic America to New York, Michigan and British America, and on open mountain 
tops in the Alleghenies to North Carolina. Also in Arctic Europeand Asia. Spring. MOUNTAIN ALDER, 
FAMILY 3. FAGACEAE Drude. BEECH FAMILY. 
Monoecious shrubs or trees, with a watery sap. Leaves alternate: blades 
simple, entire, toothed or lobed, sometimes persistent: stipules, if any, fuga- 
cious. Staminate flowers in elongated or head-like aments. Perianth of 4-7 
