140 TREES OF NORTH AMERICA 



Mature leaves covered below with appressed white silky hairs, those of flowering 

 branchlets entire or barely denticulate. 12. S. exigua (B, F, G). 



Mature leaves glabrous below, those of flowering branchlets more or less dis- 

 tinctly denticulate. 13. S. longifolia (A, F). 

 Scales of the flowers persistent, dark brown or fuscous, at least toward the apex (in <S. 



Bebbiana more or less straw-colored or tawny). 

 Stamens 2. 



Ovaries glabrous. 



Leaves more or less denticulate or serrate; styles short. 

 Base of leaf cuneate or rounded. 



Leaves acute, oblanceolate to narrowly lanceolate; filaments mostly united 

 below. 14. S. lasiolepis (G). 



Leaves mostly acuminate; filaments free. 



Branchlets glabrous, lustrous; leaves oblanceolate to narrowly obovate, 

 up to 2' in length; pedicels $'-' long; stipules small. 



15. S. Mackenzieana (A, G). 



Branchlets pubescent; leaves narrowly lanceolate to ovate-lanceolate, 4'-6' 



long; pedicels 1.5-2.5 mm. long. 16. S. missouriensis (A). 



Base of leaf mostly more or less cordate; leaves glabrous; filaments free; pedicels 



long. 17. S. pyrifolia (A). 



Leaves entire, oval to broad-obovate; branchlets villose-pubescent during their first 



season. 18. S. amplifolia. 



Ovaries pubescent (glabrous often in No. 23). 



Leaves covered with a soft dense felt-like tomentum, oblong-lanceolate to elliptic- 

 lanceolate. 19. S. alaxensis (B). 

 Leaves glabrous or more or less villose-pubescent below. 



Bracts of the flowers pale or tawny, often reddish at the tip; pedicels up to 

 ' in length; leaves elliptic-lanceolate to obovate, reticulate beneath in 

 age, pubescent or glabrate. 20. S. Bebbiana. 



Bracts of the flowers brown or fuscous. 



Stipules more or less distinctly developed; pedicels several times longer 



than the short styles. 

 Leaves elliptic-lanceolate to oblong-elliptic; mostly glabrous in age. 



21. S. discolor (A, B, F). 



Leaves oblanceolate to cuneate-obovate, covered beneath with short 

 hairs or at maturity with a gray villose-pubescence. 



22. S. Scouleriana (A, B). 



Stipules usually wanting; pedicels hardly longer than the distinct styles; 



leaves broad-elliptic to obovate-oblong, more or less grayish villose 



beneath. 23. S. Hookeriana (B, G). 



Stamens usually 1; leaves obovate-oblong, densely covered below with lustrous silvery 



white silky tomentum. 24. S. sitchensis (B, G). 



1. Salix nigra Marsh. Black Willow. 



Leaves lanceolate, long-acuminate, often falcate, gradually cuneate or rounded at 

 base, finely serrate, thin bright light green, rather lustrous, with obscure reticulate veins, 

 glabrous or often pubescent on the under side of the midribs and veins and on the short 

 slender petioles, 3'-6' long, |'-f wide; at the north turning light yellow before falling in 

 the autumn; stipules semicordate, acuminate, foliaceous, persistent, or ovoid, minute, 

 and deciduous. Flowers: aments terminal on leafy pubescent branches, narrowly cylin- 

 dric, l'-3' long; scales yellow, elliptic to obovate, rounded at apex and coated on the inner 

 surface with pale hairs; stamens 3-5, with filaments hairy toward the base; ovary ovoid, 

 short-stalked, glabrous, gradually narrowed above the middle to the apex, with nearly 

 sessile slightly divided stigmatic lobes. Fruit ovoid-conic, short-stalked, glabrous, about 

 ' long, light reddish brown. 



