166 Karl M. Wiegand and Arthur J. Eames 



d. Catkins without herbaceous bracts at the base, in flower before the leaf buds 

 begin to open. 

 e. Catkins 25-50 mm. long, not recurved ; ovary 3-4 mm. long ; capsule 



12-15 mm. long; large shrubs of wet places. 15. 5". discolor 

 e. Catkins 10-25 mm. long, mostly recurved ; ovary 2-3 mm. long ; capsule 

 7-10 mm. long ; low shrubs of dry soil. 16. S. humilis 



c. Ovary 1.5 mm. long, sessile; capsule 2-3 mm. long; young foliage glabrous 

 or glabrate, bluish green ; leaves and catkins often subopposite ; stigma 

 sessile. 17. S\ purpurea 



Key based on mature foliage 

 a. Leaves entire, glabrous, often bluish green ; apex obtuse, rounded, or barely acute 

 (see also no. 16). 

 b. Leaves green beneath. 9. S. pedicellaris 



b. Leaves glaucous beneath. 9a. S. p., var. hypoglauca 



a. Leaves toothed ; apex subacute or acuminate. 



b. Under surface of leaf more or less tomentose ; upper surface more or less 

 rugose. 

 c. Leaves elliptical or oblanceolate to obovate. 



d. Blade 2-3 (31) times as long as wide, the margin flat, the upper surface 



usually more or less pubescent. 10. S. Bebbiana 



d. Blade 3-4 times as long as wide, the margin more or less revolute, the upper 

 surface glabrous or glabrate. 16. S. humilis 



c. Leaves narrowly oblanceolate to linear-lanceolate ; margin revolute. 

 d. Upper surface of leaf hairy. 12. S. Candida 



d. Upper surface of leaf glabrous. 12a. .S\ c, var. denudata 



b. Under surface of leaf glabrous or silky; upper surface not distinctly rugose. 

 c. Leaves green or only slightly paler beneath, neither glaucous nor white-silky. 

 (/. Leaves linear-lanceolate to linear, blade 8-20 times as long as broad. 



e. Leaves tapering at base, sessile or subsessile ; teeth distant, 2-4 per cm.; 



twigs tough ; shrubs. 5. .S". longifolia 



e. Leaves rounded or obtuse at base, with a very short but distinct petiole ; 

 teeth close, 5-12 per cm.; twigs brittle at base; trees. 



1. .S\ nigra 

 d. Leaves lanceolate to ovate ; blade 2-7 times as long as broad ; twigs not 

 brittle. 

 e. Leaves, especially on the shoots, caudate-acuminate, lustrous. 

 /. Leaves and twigs glabrous. 3. 5". lucida 



/. Leaves and twigs with more or less sordid or rufous pubescence. 



3a. S. I., var. intonsa 

 e. Leaves merely acuminate. 



/. Leaves narrow, 4-10 ( 14) mm. wide, acute or tapering at base ; stipules 



lacking or ephemeral. 13. 6". pctiolaris 



f. Leaves broader (12) 15-30 mm. wide, obtuse, rounded, or subcordate, 

 rarely acute at base. 

 g. Leaves firm, lustrous; teeth very fine, (8) 10-20 per cm.; stipules 



early deciduous. 4. 5". serissima 



g. Leaves thinner, not lustrous ; teeth coarser, 3-8 per cm. ; stipules 

 usually persistent. 11. S. cordata 



c. Leaves much paler beneath, usually glaucous, sometimes white-silky. 

 d. Blade with serrations mostly lacking on lower third. 



e . Leaves subopposite, cuneate-oblanceolate, bluish green ; stipules early 



deciduous. 17. S. purpurea 



e. Leaves strictly alternate, lanceolate, elliptical, or oblanceolate, not bluish 

 green. 

 /. Leaves narrow, 4-10 (14) mm. wide; serrations sharp, minute, 6-15 per 

 cm. ; stipules early deciduous or obsolete. 13. S. pctiolaris 



