52 Flora of the Palouse Region 



82. POPULUS. 

 Trees with scaly resinous buds and round or angled twigs: 

 leaves long-petioled, broad or narrow: bracts of the aments fim- 

 briate or incised: disk cup-shaped, oblique, lobed or entire: stam- 

 inate aments dense, pendulous; pistillate aments sometimes raceme- 

 like by the elongation of the pedicels, pendulous, erect or spread- 

 ing: staminate flowers with from 4-60 stamens; filaments distinct: 

 ovary sessile; tuft of hair on the seed very conspicuous. 



Styles 2, with linear lobes: petioles flattened. P. Tremuloides. 



Styles 2-4 with dilated lobes: petioles not flattened. P. trichocarpa. 



P. tremuloides Michx. Small tree, 10-12 m. tall with smooth light bark: 

 leaves broadly ovate, snbcordate or obtuse at base, abruptly acuminate, 3-8 

 cm. long, ciliate when young, glabrate: petioles long and slender, much 

 flattened laterally: staminate aments dense, 3-5 cm. long: stamens 7-10: 

 bracts long-ciliate: pistillate aments 5-10 cm. long. Common on north hill- 

 sides and along streams. 



P. trichocarpa T. & G. Large tree, 10-30 m. tall, with rough fissured 

 bark: leaves broadly ovate, rounded at the base, acuminate, 5-12 cm. long, 

 puberulent when young, whitish beneath: petioles slender, terete, about 

 equalling the blades: staminate aments dense, the bracts long-hairy: stamens 

 50-60: pistillate aments becoming loose: capsules nearly sessile, globose, 

 puberulent or glabrate. Banks of streams, infrequent. 



83. SALIX. 

 Trees or shrubs with single-scaled buds, the scales with an ad- 

 herent membrane within: leaves short-petioled, mostly narrow, 

 with broad or minute stipules: bracts of the aments mostly entire, 

 small or minute: flowers each with one or two small glands at 

 their base: staminate aments dense, erect, spreading or drooping: 

 pistillate aments usually erector spreading: staminate flowers with 

 1 -10, mostly 2 or 5, stamens: ovary sessile or short-stipitate. 



Aments on short leafy branches. 

 Stamens 3-5. 



Petioles with glands. S. lasiaxdra. 



Petioles without glands. S. amygdaloides. 



Stamens 2: scales pale: leaves very narrow. 

 Twigs glabrous. 



Leaves pale, entire, usually pubescent beneath. 



vS. EXIGUA. 



Leaves green, denticulate, glaucous beneath. 



S. MELANOPSIS. 

 Twigs pubescent: leaves silvery-hairy on both sides. 



S. argophylla. 

 Aments sessile or nearly so, appearing with or before the leaves: stamens 2. 

 Capsules pubescent. 



vScales black: style none. S. SCOULERIANA. 



Scales black: style elongate. S. BELLA. 



Scales pink or pale. S. rostraTa. 



Capsules glabrous. 



Capsules long-pedicelled: filaments free. S. cordata. 



Capsules short-pedicelled: filaments united at the base. 



S. LASIOLEPIS. 



