Salix Salicaceae 357 



Catkins 10-15 (18) mm long; young foliage somewhat tawny 



10. iS. petiolaris. 



Catkins (15) 18-28 mm long; young foliage glabrous or white-pubes- 

 cent. 

 Anthers (dry) 0.4-0.5 mm long; young foliage white-silky; hairs of 

 bracts silky, scarcely curled or matted; twigs brittle at the base. 



11. S. sericea. 



Anthers (dry) 0.6-0.8 mm long; young foliage glabrous, or, if white- 

 pubescent, scarcely silky; hairs of the bracts curly or matted, 



scarcely silky; twigs tough at the base 18. S. cordata. 



Branchlets of previous year glabrous; anthers (dry) about 0.9 mm long 



9. S. discolor. 



KEY BASED PRIMARILY ON MATURE LEAVES AND BRANCHLETS 



A. Leaves green on both sides. 



Margins of leaves with unequally spaced, minute teeth. 



Blades linear, acute at both ends, often somewhat falcate, less than 1 cm wide, 



mostly 4-6 mm wide, rarely somewhat paler beneath 8. S. interior. 



Blades, at least some of them, linear-oblong, acute at both ends, some or many 



of them more than 1 cm wide, bluish green beneath 



8a. S. interior var. Wheeleri. 



Margins of leaves closely serrate with equally spaced teeth. 



Leaves linear-lanceolate, mostly 6-12 cm long, usually 7-10 times as long as wide, 

 rarely 2 cm wide, mostly 1-1.5 cm wide, acute or acuminate, sometimes falcate; 



teeth usually 6-10 per cm 1. S. nigra. 



Leaves not as above. 



Blades silky-pubescent on both sides, acute at the apex, subcordate at the base, 



ovate (plants along Lake Michigan) 17. S. adenophylla. 



Blades not as above. 



Petioles glandular at the summit; leaves shining above, more than 2 cm wide, 

 long-acuminate or caudate at the apex, rounded at the base. 



Blades glabrous on both sides 4. S. lucida. 



Blades mostly permanently more or less pubescent beneath with reddish 



hairs 4a. S. lucida var. intonsa. 



Petioles not glandular at the summit; leaves not shining above 



18. S. cordata. 



A. Leaves glaucous or paler beneath. 



Leaves subopposite, cuneate-oblanceolate, bluish green, very smooth; stipules 



early deciduous. (See excluded species no. 167, p. 1038.) S. purpurea. 



Leaves strictly alternate. 



Margins of leaves finely and distinctly serrate. 



Petioles glandular at the summit (sometimes obscurely so in S. alba). 



Leaves linear-lanceolate, 8-16 cm long, long-acuminate, glabrous, primary 

 veins regular, ending in the border to form a rather straight line; 

 branchlets of previous year slender, pendulous, tough. (See excluded 



species no. 162, p. 1038.) S. babylonica. 



Leaves not as above. 



Blades ovate or ovate-oblong, 4-12 cm long, closely glandular-serrate, 

 glabrous from the first, short-acuminate, rounded or subcordate at the 

 base; petioles 6-10 mm long. (See "excluded species no. 166, p. 1038.) 



S. pentandra. 



Blades not as above, mostly lanceolate. 



Leaves glossy above, glabrous, some, or most of them, more than 2 cm 

 wide, acute or acuminate at the apex, teeth (8) 10-20 per cm; pri- 

 mary veins so prominent above as to make the upper surface of dried 

 specimens rough to the touch; native shrubs, up to 4.5 m high, flower- 

 ing in late June and in July 3. S. serissima. 



