WILLOW FAMILY 61 



CapsTile scarcely rostrate, subsessile or, if stipitate, stipe shorter than the style. 

 Style evident, at least 0.5 mm. long. 



Leaves permanently silky or tomentose beneath. IX. Argenteae. 



Leaves neither silky-wlute nor tomentose beneath. X. Arcticae. 



Style none; depressed or low shrubs, with entire strongly reticulate leaves. 



XI. Reticul.\tae. 



I. Amygdalinae. 

 Bractlets entire. 



Leaves narrowly lanceolate; petioles short. 



Bark of twigs brownish ; aments long and lax ; leaf-blades broadest below the mid- 

 dle, long-acuminate. 1. S. nigra. 

 Bark of twigs Ught yellow; aments short and dense; leaf-blades usually broadest 

 at or above the middle, short-acuminate. 2. S. Wrightii. 

 Leaf-blades broadly lanceolate; petioles slender, 6-15 mm. long. 



3. S. amygdaloides. 

 Bractlets denticulate. 4. S. laevigata. 



II. Pentandrae. 



Leaves narrowly oblanceolate, acute, drying blackish; bractlets of the staminate araents 



ovate, and of pistillate lanceolate, neither toothed. 5. S. erythrocoma. 



Leaves lanceolate to ovate; bractlets of the staminate aments obovate or spatulate, 

 usually toothed; those of the pistillate aments oblong. 

 Bractlets densely white- villous ; stipe of the capsules scarcely twice as long as the 



nectaries. 6. S. serissima. 



Bractlets sparingly hairy; stipe of the capsules 3-4 times as long as the nectaries. 

 Leaves ovate-lanceolate or ovate; glands of the leaves very prominent; those on 



the petioles often stalked. 7. S. lucida. 



Leaves lanceolate; glands of the leaf-blades not very prominent; those on the 

 petioles always sessile. 

 Leaf-blades usually less than 1 dm. long, green on both sides; aments short. 



8. S. Fendleriana. 

 Mature leaf-blades often 1 dm. long, glaucous beneath; aments elongate. 



9. S. Lyallii. 

 III. Albae. 



One species. 10. S. alba. 



IV. Longifouae. 

 Capsule glabrous or slightly silky when young. 



Leaves with close serrations, glaucous and prominently veined beneath. 



11. S. melanopsis. 

 Leaves entire or with distant serrations, neither glaucous nor strongly veined beneath. 



Styles none. 



Leaves permanently silky. 



Leaves 3-5 mm. wide; ovary without a hairy swelling at the apex. 



12. S. exigua. 

 Leaves 2-3 mm. wide; ovary with a hairy swelhng at the apex. 



13. S. slenophylla. 

 Leaves glabrous in age, or nearly so. 



Leaves linear-lanceolate; bractlets ovate or obovate, obtuse. 



14. S. interior. 

 Leaves narrowly hnear; bractlets lanceolate, acute. 



15. S. linearifolia. 

 Styles evident; aments dense; bractlets densely silky. 16. S. sessilifolia. 



Capsule permanently densely pubescent. 



Stigma sessile; leaves entire or nearly so. 17. S. argophylla. 



Stigma on a distinct style, wliich is 0.5 mm. long; leaves dentate. 



18. S. macrostachya. 

 V. Cordatae. 

 Leaves wliite-tomentose or white-villous beneath. 



Leaves entire, or minutely denticulate; aments 3-4 cm. long; bractlets silky-pUose. 

 Leaves permanently appressed-silky. 19. S. Sandberg'ii. 



Leaves in age glabrous and shining, at least above. 20. S. lasiolepis. 



Leaves usually crenate, villous, 3-8 cm. long; aments 3-6 cm. long; bractlets densely 

 villous. 21. S. Hookeriana. 



Leaves glabrous or hairy, but not densely white-pubescent beneath. 

 Branches without a bloom. 



Capsule long-stipitate; stipe in fruit 1.5-6 mm. long, equalling or exceeding the 

 bractlets; style 0.5 mm. long or less. 

 Leaves dark green above; young branches not light yellow; aments on short 

 leafy branches. 

 Mature leaves rather thin, dull; length of the blade less than three times 



its width. 22. S. balsamifera. 



Mature leaves firm, dark green, shining above, pale beneath; length of 

 the blade three times the width or more. 

 Stipe in fruit 2^ times as long as the bractlets; mature leaves slightly 



serrate. 23. S. Mackenziana. 



Stipe slightly if at all exceeding the bractlets. 

 Mature leaves lanceolate, strongly serrate. 



24. S. cordala. 

 Mature leaves oblong or oblanceolate, entire. 



25. S. pedicillaris. 

 I^eaves yellowish green; young branches light yeUow; aments naked or sub- 

 tended by a few small leaves. 



