1. =Álnus incàna=, Willd. (SPECKLED OR HOARY ALDER.) Leaves 3 to 5 in. long, broadly oval or ovate, rounded at base, sharply serrate, often coarsely toothed, whitened and mostly downy beneath; stipules lanceolate and soon falling. Fruit orbicular or nearly so. A shrub or small tree, 8 to 20 ft. high, with the bark of the trunk a polished reddish green; common along water-courses north of 41° N. Lat.; sometimes cultivated. [Illustration: A. serrulàta.] 2. =Álnus serrulàta=, Willd. (SMOOTH ALDER.) Leaves 2 to 4½ in. long, thickish, obovate, acute at base, sharply and finely serrate, green both sides, smooth or often downy beneath; stipules yellowish green, oval, and falling after 2 or 3 leaves have expanded above them. Fruit ovate. Rather a shrub than a tree, 6 to 12 ft. high, common along streams south of 41° N. Lat. In the Southern States it sometimes forms a tree 30 ft. high. [Illustration: A. marítima.] 3. =Álnus marítima=, Muhl. (SEASIDE ALDER.) Smooth; leaves oblong-ovate to obovate, with a tapering base, sharply serrulate; petiole slender; color bright green, somewhat rusty beneath. Flowering in the autumn. Fruiting catkin large, ¾ to 1 in. long, ½ in. thick, usually solitary, ovoid to oblong. A small tree, 15 to 25 ft. high. Southern Delaware and eastern Maryland, near the coast. [Illustration: A. glutinòsa.] 4. =Álnus glutinòsa=, L. (EUROPEAN ALDER.) Leaves roundish, wedge-shaped, wavy-serrated, usually abrupt at tip, glutinous; sharply and deeply incised in some varieties. Fruit oval, ½ in. long. A medium-sized tree, 25 to 60 ft. high, of rapid growth, often cultivated under several names; the most important being vars. _laciniata_ (cut-leaved), _quercifolia_ (oak-leaved), and _rubrinervis_ (red-leaved). [Illustration: A. cordifòlia.] 5. =Álnus cordifòlia=, Ten. (HEART-LEAVED ALDER.) Leaves heart-shaped, dark green and shining. Flowers greenish-brown, blooming in March and April, before the leaves expand. A large and very handsome Alder, 15 to 20 ft. high, growing in much dryer soil than the American species. Cultivated from southern Europe. Hardy after it gets a good start, but often winter-killed when young. GENUS =85. CÓRYLUS.= Low trees and large shrubs with simple, alternate, deciduous, doubly serrate, straight-veined leaves. Flowers insignificant, in catkins in early spring. Fruit an ovoid-oblong bony nut, inclosed in a thickish involucre of two leaves with a lacerated frilled border; ripe in autumn. * Leafy bracts of fruit forming a bottle-shaped involucre 2. * Leafy bracts not bottle-shaped. (=A.=) =A.= Involucre much longer than the nut 1. =A.= Involucre but little longer than the nut 3. [Illustration: C. Americàna.]