340 SALICACEAE 
young, soon glabrous or nearly so: winter buds broadly ovoid, less than 1 cm. long: leaves 
numerous ; blades broadly ovate, three-nerved, 10-15 cm. long, or longer on young 
plants, usually acutish, crenate-serrate, sometimes floccose beneath, rounded to subcordate 
at the base, long-petioled : staminate aments 5-10 cm. long, 18-25 mm. thick : stamens 
12-20 : stigmas with much thickened and dilated lobes: mature pistillate aments 3-10 cm. 
long, raceme-like : capsules ovoid, 8-12 mm. long, acute, on pedicels about 1 cm. long. 
In swamps or on river banks, Connecticut and Indiana to Arkansas, Georgia and Louisiana. 
9. Populus alba L. A tree, with a maximum height of about 35 m. and a trunk 
diameter of 1.5 m. Bark light gray or whitish: buds and twigs tomentose : leaf-blades 
silvery white, tomentose beneath, deep green above, ovate or suborbicular, usually 3-5- 
lobed, 5-10 cm. long, rounded or cordate at the base ; petioles shorter than the blades : 
staminate aments 3-5 cm. long: anthers purple: pistillate aments about twice as long as 
the staminate : stigmas small and narrow. 
In eultivated grounds and along roadsides, rather commonly established throughout eastern 
North Ameriea. Native of Europe and Asia. 
2. SALIX L. 
Trees and shrubs, with dark more or less flaky bark. Twigs slender and flexible: buds 
with a single scale each. Leavesalternate: blades pinnately veined, usually finely toothed, 
petioled or nearly sessile : stipules foliaceous or obsolete. Flowers in aments, pollination 
entomophilous. Aments usually dioecious : bracts entire, more or less clasping at the base, 
with one or more glands at the base of the flower. Stamens usually 2 (1—7) : anthers yel- 
low or reddish. Ovary more or less stipitate: stigmas often divided and filiform. Ovules 
anatropous. Capsules dehiscent at the apex into two valves. The plants flower in the 
early or late spring. 
Capsules glabrous, at least at maturity. 
Stamens 3-7: filaments pubescent at the base: bracts yellow, caducous. 
Pedicels 3-5 times as long as the glands. 
Leaf-blades green on both sides, but often paler beneath. 
Leaf-blades 2-5 em. long: bracts of staminate aments acute or acutish. 
Leaf-blades 6-15 em. long: bracts of staminate aments blunt. 
Leaves with narrowly lanceolate blades. 
Bracts of priate aments about 1mm. long: leaf-blades slender- 
1. S. marginata. 
petioled. 2. S. nigra. 
Bracts of pistillate aments fully 2 mm. long: leaf-blades short- 
petioled. 4. S. longipes. 
Leaves with broadly lanceolate blades and slender petioles. 3. S. amygdaloides. 
Leaf-blades glaucous or silvery pubescent beneath. 4. S. longipes. 
Pedicels about twice as long as the glands. 5. S. fragilis. 
Stamens 2. 
Filaments pubescent at the base: bracts caducous. 
Pedicels 1-3 mm. long at maturity. 
Styles wanting: leaves with linear or linear-lanceolate blades. 
Leaf-blades finely and mostly permanently silky. 11. S. luteosericea. 
Leaf-blades glabrous, or sometimes coarsely silky when young. 
Leaves with linear-lanceolate blades: bracts ovate or obovate, 
obtuse. 12. S. interior. 
Leaves with narrowly linear blades: bracts lanceolate, acute. 13. S. linearifolia. 
Styles manifest, but short: leaves with lanceolate blades. 5. S. fragilis. 
Pedicels less than 1 mm. long at maturity : stigmas sessile. 
Branches erect or spreading: leaf-blades lanceolate. 6. S. alba. 
Branches drooping : leaf-blades linear or linear-lanceolate. 7. S. Babylonica. 
Filaments glabrous: bracts persistent. 
Leaf-blades less than 3 times as long as broad. 8. S. Floridana. 
Leaf-blades fully 3 times as long as broad. 
Bracts pale: leaf-blades green on both sides. 9. S. cordata. — . 
Braets fuscous : leaf-blades glaucous beneath. 10. S. Missouriensis. 
Capsules variously pubescent. 
Filaments distinct. 
Leaf-blades glabrous or sparingly pubescent beneath. 
Leaves with linear, linear-lanceolate or lanceolate blades. 
Filaments pubescent : capsules nearly glabrous at maturity. k 
Leaf-blades finely and mostly permanently silky. 11. S. luteosericea. 
Leaf-blades glabrate, often coarsely silky when young. 
Leaves with linear-lanceolate blades: bracts ovate or obovate, 3 
obtuse. 12. S. interior. |, 
Leaves with narrowly linear blades: bracts lanceolate, acute. 13. S. linearifolia- 
Filaments glabrous: de iria ubescent. 14. S. petiolaris. 
Leaves with oblong or oblong-lanceolate blades, or these sometimes : 
broadest above the middle. 15. S. discolor. 
Leaf-blades densely pubescent beneath with white hairs. : 
Leaves with blades 2-5 em. long: fruiting aments 1-1.5 em. long. 16. S. tristis. 
Leaves with blades 6-10 em. long: fruiting aments 2-3 em. long. 
Filaments, and usually the anthers, united. 
s. humilis. 
S 
\. purpurea. 
