346 FAGACEAE 



2. Betula lenta L. A forest tree reaching a maximum heiglit 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 cm. long ; bracts ovate, about 2.5 cm. long, naked like the suborbicular bractlets: 

 pistillate aments about 1.5 cm. long, accrescent into cones 2-3 cm. 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, Xcwfoundland to Minnesota, Tennessee and Florida. Sweet, Cherry or Bl.\ck Birch. 



3. Betula lutea ^lichx. f. A forest tree, reaching a maximum height of about 30 m. 



and a maximum trunk diameter of 2 m. 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, romided 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. 



In woods, Newfoundland to Manitoba and the mountains of Georgia. Gray Birch. Yellow 

 Birch. 



2. ALNUS L. 



Shrubs or trees, with a pale astringent bark, and terete branchlets. Staminate flowers 

 in drooping aments. Calyx usually 4-lobed or irregularly 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, tlie 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 rugosa ( Du Roi ) K. Koch. A shrub or small tree reaching a height of 



about 13 m. and a trunk diameter of 15 cm. 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 at the 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, Florida and Texas. Winter 

 and spring. Smooth Alder. 



2. Alnus Alnob6tula (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 cm. long, rather slender, usually 

 appearing with the leaves : pistillate aments developing ovoid or oblong, long-peduncled 

 cones, 1-2 cm. long, their bracts flabellate, undulately-lobed at the top : nuts oblong or 

 obovoid, 2 mm. long, furnished with orbicular-obcordate wings. [A. vlridis (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 Europe and Asia. Spring. Mountain Aldek. 



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 



