358 Salicaceae Salix 



Leaves not as above; introduced trees, flowering in May and early 

 June (the following two species difficult to separate). 

 Serrations of blades rather coarse, generally 3-8 per cm and 0.4-1 

 mm deep; blades rather firm, glabrous or appressed-pubescent, 

 especially beneath, acuminate or long-acuminate, the primary veins 

 so prominent above as to make the upper surface of dried specimens 

 rough to the touch; branchlets of previous year brittle at the 



base 7. S. fragilis. 



Serrations of blades generally 6-12 per cm and 0.1-0.4 mm deep; 

 blades thinner than the preceding, smooth to the touch above, 

 usually more or less appressed-pubescent or glabrous, acute or 

 acuminate at apex. 



Leaves distinctly silky beneath; branchlets greenish 6. S. alba. 



Leaves subglabrous beneath; branchlets yellowish 



6a. S. alba var. vitellina. 



Petioles not glandular (not to be confused with glands at the base of the 



blade). 



Leaves glabrous on both sides. (No. 18 often so glabrous that it might be 



wrongly placed here.) 



Blades small, broadest about the middle, usually 5-10 mm wide, rarely 



up to 15 mm wide, linear-lanceolate to lanceolate, teeth generally 5 or 6 



per cm; mostly acuminate 10. S. petiolaris. 



Blades larger, broadest above or below the middle, mostly (10) 15-30 mm 



wide, long-acuminate, obtuse or acute. 



Blades broadest below the middle, lanceolate to broadly lanceolate or 



ovate-lanceolate, long-attenuate at the apex, broadly cuneate to 



rounded at the base, teeth mostly 7-12 per cm of margin measured 



midway between base and apex; stipules rarely present; petioles 



mostly 6-15 mm long 2. S. amygdaloides. 



Blades generally broadest above the middle, or below the middle in some 

 forms of leaves, usually oblanceolate to ovate or elliptic-lanceolate, 

 or ovate on coppice shoots, acute at the apex, rarely acuminate, 

 broadly cuneate or rounded at the base, cordate in the ovate type 

 of leaves; teeth mostly 3-6 per cm; stipules usually present, especially 

 on vegetative branchlets, subcordate to broadly reniform, 3-10 mm 



long, acute; petioles mostly 3-10 mm long 19. S. glaucophylla. 



Leaves more or less pubescent, at least some of them so. 



Leaves white silky-pubescent beneath, at least some of them more or less 

 pubescent on one or both sides, especially along the midrib and toward 

 the base on the lower surface, and pubescent at the apical end on the 

 upper surface of terminal leaves. 

 Blades rather thin, small, narrow, linear-lanceolate to lanceolate, mostly 

 5-8 cm long and 5-10 mm wide, rarely up to 14 mm wide; pubescence, 

 when present, usually tawny, rarely all whitish; teeth of margins 

 usually 5 or 6 per cm; petioles 4-10 mm long; stipules none; branch- 

 lets more or less fascicled 10. S. petiolaris. 



Blades mostly longer, wider, and thicker than the preceding. 



Leaves silvery-pubescent beneath, the pubescence strongly or loosely up- 

 wardly appressed or sometimes glabrate or glabrous beneath, nar- 

 rowly to broadly lanceolate or somewhat oblanceolate, usually about 

 5 times as long as" wide, rounded or narrowed at the base, the lateral 

 veins both above and beneath usually conspicuous. 

 Lower surface of leaves strongly upwardly appressed-pubescent, 

 silvery (rarely somewhat glabrate in age) ; blades strongly taper- 

 ing at the base; stipules soon deciduous 11. S. sericea. 



Lower surface of leaves loosely appressed-pubescent when young, 

 usually becoming glabrous or glabrate at maturity or remaining 



