BIRCH FAMILY 205 



Nut bordered on each side with a membranous wing-margin, fully as broad as the nut; 

 twigs resinous-granulifcrous; stamens 4. 

 Leaves irregularly serrate, usually very oblique at the base, slightly paler beneath. 



1. A. fruticosa. 

 Leaves incised and sharply double-serrate, green on both sides. 



2. A. sinuata. 

 Nut merely acute-margined. 



Leaves distinctly lobod and doubly serrate; stamens 4. 



Mature leaves pubescent, especially beneath, usually glaucous beneath; bark 



wliite-speckled. 3. A. incana. 



Mature leaves glabrous, e.xcept on the veins beneath and in their axils, green on 

 both sides; bark not speckled. 4. A. tenuifnlia. 



Leaves not lobed, merely sinuate and glandular-dentate; stamens 1-3, usually 2. 



5. A. rhombifolia. 



1. A. fruticosa Rupr. A tree sometimes 12 m. high; 3'oung twigs minutely 

 puberulent, becoming brown and shining; leaf-blades broadly ovate, 6-10 cm. 

 long, short-acuminate or obtuse; staminate aments in pairs, 10-12 cm. long; 

 filaments longer than the caly.x; pistillate aments elliptic, 12-15 mm. long; nut 

 oval, about 2 mm. long. Al.\.ska Alder. Along streams: Alaska — -Yukon — ■ 

 B.C. — Wash.; e Siberia. Subnionl. My-Je. 



2. A. sinuata (E. Regel) Rydb. A shrub 1-4 m. high; young twigs brown or 

 greenish, glabrous or nearly so; leaf -blades ovate, 5-10 cm. long, acute or short- 

 acuminate at the ape.x, acute, rounded or rarely subcordate at the base, thin, 

 glabrous or nearly so; staminate aments 3-8 cm. long; filaments not exceeding 

 the calyx; pistillate aments rounded-ellipsoid, 12-15 mm. long; nut elliptic. 

 Mountain Aldeh. Mountain streams: B.C. — Ore.— Wyo. — 'Alta. Mont. 

 My-Jl. 



3. A. incana (L.) Moench. Shrub or small tree, rarely 6 m. high; leaf- 

 blades broadly elliptic to ovate, rounded at the base, sharply and doubly serrate, 

 dark green above, downy and ferruginous or glaucous, prominently veined hi- 

 neath, 5-13 cm. long; staminate aments 3-8 cm. long, the pistillate in fruit 1-1.5 

 cm. long; nut orbicular, thick-margined. Speckled Alder. Swamps and along 

 streams: Newf. — -Pa. — Neb. — Sask. ; Eurasia. Boreal. Ap-My. 



4. A. tenuifolia Nutt. A tall shrub or small tree, sometimes 8-10 m. high; 

 twigs pubescent when young; leaf-blades ovate or oval, obtuse or acute at the 

 apex, rounded or subcordate at the base, 5-10 cm. long; staminate aments 2.5- 

 4.5 cm. long, filaments equalling the calyx; pistillate aments when ripe 1-2 cm. 

 long, ellipsoid; nut 2.5 mm. long. A. incana virescens S. Wats. River Alder. 

 Along streams: Alaska — Calif. — -N.M. — Yukon. Siibmont. — 'Mont. Ap-My. 



5. A. rhombifolia Nutt. A tree sometimes 25 m. high; young twigs green 

 and pubescent; leaf-blades oval or rarely ovate, 5-12 cm. long, hairy on both 

 sides when young, of ten glabrate in age and dark green above, paler beneath; 

 staminate aments 6-15 cm. long, yellow; pistillate aments ellipsoid, 1.5-2 cm. 

 long; nut oval, about 2.5 mm. long. Along streams: B.C. — -Ida. — •Calif. Sub- 

 mont. D-Ja. 



Family 33. CORYLACEAE. Hazelnut Family. 



Monoecious trees or shrubs, with simple alternate leaves. Staminate 

 aments elongate, drooping, each bract subtending a single flower; calyx 

 wanting; filaments distinct, branched at the apex. Pistillate aments short; 

 bracts foliaceous at maturity, each subtending 2 or 3 flowers; calyx present, 

 sometimes represented by a cup. Fruit 1-3 nuts, enclosed in the bracts. 

 iSeeds solitary b}' suppression. 

 Pistillate flowers many in a cylindric ament; nuts small, enclosed in a bladdery bract. 



1. OSTRYA. 



Pistillate flowers few in a head-like ament; nut large, in a leaf-like involucre. 



2. CORYLUS. 



1. OSTRYA (Mich.) Scop. Ironwood, Hop-hornbeam. 



Trees with close-grained, hard wood and scaly bark. Staminate aments 

 clustered, drooping; bracts subtending 3-14 stamens; filaments very short, 



