WILLOW FAMILY 187 



9. P. hastata Dode. A tree 10-20 m. high, with gray trunk and branches; 

 petioles 3-4 cm. long, glabrous; leaf-blades ovate, ovate-deltoid, or subcordate, 

 dark green above, pale beneath, mostly acuminate, rounded or cordate at the 

 base, crenulate, 6-10 cm. long; aments 5-12 cm. long; cup 4-5 mm. wide. Val- 

 leys: Alta. — Mont. — Ida. Submont. — Mont. Ap-Je. 



10. P. balsamifera L. A tree sometimes 25 m. high, with reddish gray 

 trunk and light brown or gray branches; petioles 2-5 cm. long; leaf-blades ovate 

 to ovate-lanceolate, dark green and shining above, pale beneath, acute or acum- 

 inate at the apex, rounded or cuneate at the base, crenulate, 7-12 cm. long; 

 aments 5-10 cm. long. Balsam Poplar. Along streams and lakes: Newf. — 

 N.Y. — Colo. — Nev. — Alaska. Submont. — -Mont. Ap. 



11. P. candicans Michx. A tree sometimes 30 m. high, with gray trunk 

 and round branches, pubescent when young, in age glabi'ate; petioles pubescent 

 or ciliate; leaf-blades broadly ovate, acute or acuminate at the apex, cordate or 

 truncate at the base, 6-15 cm. long, 3-12 cm. wide, dark green above, pale 

 beneath, crenate; aments 6-12 cm. long; capsule oblong-ovoid, smooth, short- 

 stalked. Balm of Gilead. Roadsides and river banks: Newf. — N.J. — S.D.^ 

 Alta. — Alaska. Boreal. Ap-My. 



12. P. Tweedyi Britton. A small tree, with yellowish twigs; petioles stout, 

 5-12 mm. long; leaf-blades ovate to nearly round, acute, finely crenate, cordate 

 or rounded at the base, 3-7 cm. long, dark green above, paler beneath; aments 

 3-4 cm. long, in fruit 6 cm. ; capsules ovoid, densely papillose, 4 mm. long; pedicels 

 about 1 mm. long. Cottonwood. River bottoms: Wyo. Submont. 



13. P. angustifolia James. A slender tree, sometimes 20 m. high, with 

 upright branches and greenish bark; petioles 6-12 mm. long; leaf -blades lanceo- 

 late to ovate, acute or gradually acuminate at the apex, cuneate, rounded or 

 rarely subcordate at the base, green above, paler beneath, finely crenate, 5-12 

 cm. long; aments 2-6 cm. long; capsule ovoid, rugose. P. coloradensis Dode. 

 P. fortissima Nels. & Macb. Narrow-leaved or Black Cottonwood. Along 

 streams: Sask. — Neb. — N.M. — Ida.; n Mex. Plain — Mont. Ap-My. 



14. P. alba L. A large tree, sometimes 35 m. high, with light gray bark; 

 petioles shorter than the blades, subterete; leaf -blades densely white-tomentose 

 on both sides, becoming glabrate and dark green above, broadly ovate or or- 

 bicular in outline, 3-5-lobed and irregularly toothed, 6-10 cm. long; aments 

 3-6 cm. long; capsules elliptic, subsessile. White or Silver Poplar. In 

 yards and along roadsides: N.B. — Va. — N.M. — Utah; cult, and escaped, native 

 of Eurasia. Mr-My. 



2. SALIX (Tourn.) L. Willow. 



Trees or shrubs, usually with flaky bark and slender, flexible twigs; bud of 

 only one scale. Leaves alternate, petioled or subsessile, pinnately veined, 

 usually finely toothed. Bractlets of aments entire or rarely denticulate, with 

 one or more gland-like nectaries at the base of the stamens or the pistil. Sta- 

 mens 1-7, usually 2: anthers usually yellow. Ovary more or less stipitate; 

 stigmas 2, often 2-cleft, with narrow branches. Capsule dehiscent at the apex 

 into 2 valves. 



Capsule glabrous, or slightly silky when young in nos. 12, 14, and 16. 



Filaments hairy, at least below; bractlets caducous, light yellow; style very short, 

 obsolete, or none, evident only in nos. 16 and 18; aments in all ours on short 

 leafy branches. 

 Stamens .3-7; stipe slender, 2-5 times as long as the nectaries. 



Petioles without glands; leaves remotely serrulate, thin. I. Amygdalinae. 



Petioles with glands; leaves densely glandular-serrate, firmer. 



II. Pentandrae. 

 Stamens 2 ; stipes usually very short. 



Leaf-blades lanceolate, acuminate. III. Alb.-ve. 



Leaf-blades linear or linear-lanceolate, acute, rarely acuminate. 



IV. LONGIFOLLIE. 



Filaments glabrous; bractlets persistent, rarely light yellow. 



Trees, or erect or ascending shrubs, several dm. high; leaf-blades more than 1 cm. 



long; style evident. V. Cordatae. 



Depressed prostrate shrubs, 1-3 cm. high; leaf-blades less than 1 cm. long; style 



none. VI. Retusae. 



