Subclass 2. DICOTYLEDONES. 



Family 30. SALICACEAE. Willow Family. 



Bractlets incised; flowers with a cup-shaped disk; stamens usually more than 10; stigmas 

 expanded; winter-buds with several scales 1. Populus. 



Bractlets entire or denticulate; flowers with one or more glands; stamens 2-7, in most 

 species only 2; stigmas narrow; winter-buds with but 1 scale each. 2. S.\Lrx. 



1. POPULUS (Tourn.) L. Poplar, Cottonwood, Aspen. 



Leaves not white-tomentose beneath, toothed or rarely entire. 

 Petioles strongly flattened laterally. 



Leaves suborbicular, acute or very short-acuminate, finely crenate or subentire. 

 Leaf-blades with 2 conspicuous glands beneath at the base. 



I. P. cercidiphylla. 

 Leaf-blades not glandular at the base. 2. P. iremuloides. 



Leaves broadly deltoid, cordate, or ovate, abruptly acuminate, coarsely toothed, 

 especially about the middle. 

 Cup of the pistillate flowers 6-8 mm. broad. 



Pedicels equalling or exceeding the capsules ; leaf-blades longer than broad ; 



teeth few, less than 10 on each side. .3. P. Wislizeni. 



Pedicels shorter than the capsules ; leaf-blades usually broader than long ; 

 teeth more than 10 on each side, sometimes obscure. 



4. P. Fremontii. 

 Cup of the pistiUate flowers less than 5 mm. broad; teeth of the leaves many, 



more than 10 on each side; pedicels shorter than the capsule. 

 Leaves flabellate-cordate, with a broad, concave, entire sinus. 



5. P. Sargentii. 

 Leaf-blades ovate, rounded or cuneate at the base, which is more or less 



toothed ; only the blades of the young shoots cordate. 



6. P. Besseyana. 

 Petioles terete or nearly so. 



Petioles at least half as long as the blades; blades cordate, ovate, or broadly lan- 

 ceolate. 

 Leaves green on both sides, abruptly long-acuminate. 7. P. acuminata. 



Leaves paler beneath, acute or somewhat acuminate. 

 Fruit sessile, usually 3-carpellary. 



Ovary and capsule densely pubescent, subglobose. 8. P. trichocarpa. 

 Ovary and fruit glabrous, but slightly warty, ovoid. 



9. P. hastata. 

 Fruit pedicelled, 2-carpellary, glabrous; capsule ovoid. 



Twigs, petioles, and veins glabrous. 10. P. balsamifera. 



Twigs, petioles, and veins of the lower surface of the leaves more or less 

 pubescent. 11. P. candicans. 



Petioles about one-third as long as the blade or less. 



Leaves cordate at the base. 12. P. Tueedyi. 



Leaf-blades lanceolate, usually acute at the base. 13. P. angustifolia. 



Leaves white-tomentose beneath, often lobed. 14. P. alba. 



2. SALIX (Tourn.) L. Willow. 



Capsule glabrous, or slightly silky when young in nos. 12, 14, and 16. 



Filaments hairy, at least below; bractlets caducous, light yellow; style very short, 

 obsolete, or none, evident only in nos. 16 and 18; aments in all ours on short 

 leafy branches. 

 Stamens 3-7; stipe slender, 2-5 times as long as the nectaries. 



Petioles without glands; leaves remotely serrulate, tliin. I. Amygd.vlinae. 



Petioles with glands; leaves densely glandular-serrate, firmer. 



II. Pent.\ndr.\e. 

 stamens 2; stipes usually very short. 



Leaf-blades lanceolate, acuminate. III. Alb.\e. 



Leaf-blades linear or linear-lanceolate, acute, rarely acuminate. 



IV. LONGIFOLU.E. 



Filaments glabrous; bractlets persistent, rarely light yellow. 



Trees, or erect or ascending shrubs, several dm. high; leaf-blades more than 1 cm. 



long; style evident. V. Cordatae. 



Depressed prostrate shrubs, 1-3 cm. high; leaf-blades less than 1 cm. long; style 

 none. VI. Retusae. 



Capsule hairy. 



Filaments hairy; bractlets caducous; leaf-blades linear to lanceolate, not very veiny. 



IV. Longifoliae. 

 Filaments glabrous, or if somewhat hairy, leaf-blades oval or orbicular, very veiny; 

 bractlets persistent. 

 Capsule rostrate, distinctly stipitate; style none or short, always shorter than the 

 stipe. 

 Stipe equalling or exceeding the bractlets; style 0.5 mm. long or less. 



VII. Rostratae. 

 Stipe shorter than the bractlets; style usually 1 mm. long. 



VIII. Capre.ie. 



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