330 FLORA. 



Nut bordered by a membranous wing on each side. i. A. Alnobetula. 



Nut acute-margined, wingless. 



Leaves obovate, broadly oval or suborbicular, dull; aments expanding long before 

 the leaves. 



Leaves finely tomentose or glaucous beneath. 2. A. incana. 



Leaves green, glabrous or sparingly pubescent beneath. 



Leaves finely serrulate; foliage not glutinous; native. 3. A. rugosa. 

 Leaves dentate-serrate; twigs glutinous; introduced tree. 4. A. glutinosa. 

 Leaves oblong, bright green and shining above; aments expanding in autumn. 



5. A. maritima. 



1. Alnus Alnobetula (Ehrh.) K. Koch. GREEN OR MOUNTAIN ALDER. 

 (I. F. f. 1220.) A shrub, 0.5-3.5 m. high, the young foliage glutinous and more 

 or less pubescent. Leaves oval or ovate, sharply and irregularly serrulate or 

 incised-serrulate, when mature dark green and glabrous above, usually pubescent 

 on the veins beneath, 5-13 cm. long; petioles 8-25 mm. long; aments expanding 

 with the leaves, the staminate slender, naked, 3-6 cm. long, the pistillate from 

 scaly buds, oblong or ovoid-oblong, slender-peduncled, becoming 12-14 mm ' l n g 

 in fruit, their bracts irregularly 5 -toothed; nut oblong, the thin wing about as 

 broad as the body. Newf. to Alaska, Mass., N. Y., Mich, and Br. Col., and in 

 the higher Alleghanies of Va. and N. Car. Also in Europe and Asia. June. 



2. Alnus incana (L.) Willd. SPECKLED OR HOARY ALDER. (I. F. f. 1221.) 

 A shrub, or rarely a small tree, the young shoots pubescent. Leaves oval or ovate, 

 usually acute, finely serrulate or dentate, dark green above, pale or glaucous and 

 pubescent, at least on the veins beneath, 5-13 cm. long, the veins prominent on the 

 lower surface; petioles 825 mm. long; aments appearing from naked buds, the 

 staminate 3-8 cm. long, the pistillate ovoid, 1-1.5 cm - l n g * n fruit, their bracts 

 5-toothed; nut orbicular, coriaceous-margined. In wet soil, Newf., N. W. Terr., 

 S. N. Y., Penn. and Neb. Also in Europe and Asia. April-May. 



3. Alnus rugosa (DuRoi) K. Koch. SMOOTH ALDER. (I. F. f. 1222.) A 

 shrub, or sometimes a small tree, the bark smooth, the younger shoots somewhat 

 pubescent. Leaves green on both sides, obovate or oval, mostly obtuse and 

 rounded, sharply and minutely serrulate, when mature glabrous above, usually 

 pubescent on the veins beneath, 7-13 cm. long; aments appearing from naked 

 buds, the staminate 5-10 cm. long, the pistillate ovoid, 1-2 cm. long in fruit; nut 

 ovate, narrowly coriaceous-margined. In wet soil, or on hillsides, Me. to Ohio, 

 Minn., Fla. and Tex. March-April. 



4. Alnus glutinosa (L.) Medic. EUROPEAN ALDER. (I. F. f. 1223.) A tree, 

 the bark smooth, the foliage glutinous. Leaves broadly oval, orbicular or obovate, 

 thick, dark green, dull, often obtuse at both ends, dentate and the teeth denticulate, 

 glabrous above, pubescent on the veins beneath, 5-13 cm. long; aments, the stam- 

 inate 7-10 cm. long, the pistillate ovoid-oblong, 1-2 cm. long in fruit; nut wing- 

 less, coriaceous-margined. In wet places, S. N. Y. and N. J., escaped from cultiva- 

 tion. Native of Europe. April. 



5. Alnus maritima (Marsh.) Muhl. SEASIDE ALDER. (I. F. f. 1224.) A 

 small tree, glabrous or nearly so throughout. Leaves oblong, ovate-oblong or ob- 

 ovate, firm, acute at both ends, bright green and shining above, pale green and dull 

 beneath, sharply serrulate, 5-10 cm. long; aments unfolding long after the leaves, 

 the staminate 2.56 cm. long, the pistillate oblong, 1.52.5 cm. long; nut oblong- 

 obovate, wingless, coriaceous-margined. In wet soil, S. Del. and E. Md. ; also in 

 the Ind. Terr. Aug. -Sept. 



Family 2. FAGACEAE Drude. 

 Beech Family. 



Trees or shrubs. Leaves alternate, petioled, pinnately veined, the 

 stipules, if any, deciduous. Flowers small, monoecious, the staminate in 

 aments, or capitate, the pistillate subtended by an involucre of partly or 

 wholly united bracts, which becomes a bur or cup. Petals none. Stam- 

 inate flowers with a 4~7-lobed perianth and 4-20 stamens; filaments 

 slender, distinct, simple; anther-sacs adnate, longitudinally dehiscent. 



