22(21). Leaves commonly broadly lanceolate (less than 6 times as long as wide), 

 usually only moderately acuminate, glaucous but ordinarily not 

 silvery-white beneath 8. S. laevigata. 



22. Leaves commonly narrowly lanceolate (6 or more times as long as wide), very 



long- and sharp-acuminate, silvery-white beneath 



7. S. Bonplandiana. 



23(19). Bases of the leaves rounded or subcordate (seldom cuneate); stamens 2, 

 the filaments glabrous (24) 



23. Bases of the leaves cuneate or attenuate (sometimes rounded in 5. laevigata), 



the blades often shiny above and very glaucous beneath (25) 



24(23). Bark of the twigs yellow or brown; leaves oblong-lanceolate to linear- 

 lanceolate, yellowish-green and usually not glossy above, moderately 

 glaucous beneath 18. S. hgida. 



24. Bark of the twigs reddish-brown to dark-purple (plum-colored); leaves elliptic 



(often broadly so), dark-green and slightly glossy above, strongly 

 glaucous beneath; stipules large, usually persistent. ...20. S. monticola. 



25(23). Leaves prevailing oblanceolate to broadly obovate (26) 



25. Leaves prevailingly lanceolate to oblong-lanceolate (27) 



26(25). Capsules hairy; leaves commonly obovate 24. S. Scouleriana. 



26. Capsules glabrous; leaves commonly oblanceolate 17. S. lasiolepis. 



27(25). Branchlets commonly dark-purple (plum-colored) and very glaucous; 

 filaments glabrous 16. S. irrorata. 



27. Branchlets yellow to dark-brown, not or but slightly glaucous; filaments hairy 



toward base 8. 5. laevigata. 



1. Salix nigra Marsh. Black willow, sauz. Fig. 387. 



Tree to 20 m. tall, sometimes with several trunks and when young somewhat 

 shrubby, with flaky dark-brown to blackish bark; branchlets and twigs brittle at 

 base but tough and flexible above, soon glabrate; stipules semicordate, acute, 

 glandular-serrulate, to 12 mm. long, caducous; leaves with pubescent to glabrous 

 petioles 4—10 mm. long; blades (when mature) linear to narrowly lanceolate, 

 acuminate-attenuate, broadly to narrowly cuneate at base, often falcate, 5-15 cm. 

 long, 5-15 mm. wide, becoming glabrous, deep green on both surfaces, glandular- 

 serrulate; aments coetaneous, terminating leafy shoots, slender-cylindric, 2-8 cm. 

 long; scales obovate, yellowish, crisp-villous on inner surface, caducous; staminate 

 flowers with 2 basal glands; stamens 3 to 5, the free arching filaments pubescent 

 below; pistillate flowers with 1 basal gland; style nearly obsolete; capsules ovoid- 

 conical, fulvous, glabrous, 3-5 mm. long. 



In alluvial soils along streams and in wet meadows, also about ponds, lakes and 

 other water bodies, in Okla. (Blaine, Caddo, Seminole and Texas cos.) and in the 

 e. two third of Tex., w. to the 101st Meridian and s. to Cameron Co., spring; 

 N.B. and N.E., s. to Fla., w. to s. Minn., s.e. Neb, e. Kan., Okla. and Tex.; also 

 n.e. Mex. 



Var. nigra and var. Lindheimeri Schneid, are distinguished in the key. In addi- 

 tion, var. Lindheimeri further differs from var. nigra in its usually narrower 

 leaves that are at least more attenuate at the base. Its young branchlets and 

 petioles are also glabrous or become so very soon. 



2. Salix Humboldtiana Willd. 



Very similar to S. nigra var. Lindheimeri, but differs from that species in having 

 sculptured markings on the ovoid to ovoid-oblong or ellipsoid glabrous capsules 

 and in lacking a miniature shoot from the axis of the top peduncle leaf. Also, the 

 stipules are said to be glandless. Salix nigra has ovoid-conical unsculptured cap- 



757 



