FLORA OF THE DISTRICT OF ^COLUMBIA. 133 



Catkins sessile, appearing before the leaves; capsule pubescent or woolly. Scales of 

 the catkins black, long-hairv. 

 Catkins slender; capsule 3-4 mm. long, silvery-pubescent; leaves silvery-silky and 



glaucous beneath; treelike shrub 8. S. sericea. 



Catkins stout; capsule 6-8 mm. long, woolly; leaves oblanceolate, woolly beneath; 

 low shrubs. 

 Catkins oval-oblong, 1-3 cm. long; leaves broadly oblanceolate, 5-8 cm. long; 



shrub 1 meter high or more 9. S. humilis. 



Catkins nearly spherical, 0.5-1.5 cm. long; leaves narrowly oblanceolate, 2-5 

 cm. long; shrub about 0.5 meter high 10. S. tristis. 



KEY TO SPECIMENS WITH LEAVES ONLY. 



Leaves glabrous when fully grown. 

 Leaves green on both sides. 



Ijcaves linear or broadly linear, remotely and minutely toothed. . .1. S. interior. 



Leaves narrowly lanceolate, closely serrate 2. S. nigra. 



Leaves pale or glaucous beneath. 



Twigs long, slender, pendulous; leaves linear-lanceolate, minutely serrate. 



6. S. babylonica. 

 Twigs short, not pendulous; leaves lanceolate. 



Stipules very small, inconspicuous, early deciduous. 



Petioles glandular; leaves coarsely serrate 4. S. fragilis. 



Petioles usually without glands; leaves finely serrate 5. S. alba. 



Stipules large, conspicuous, usually persistent, especially on young shoots. 



Leaves narrowly lanceolate, very glaucous beneath 3. S. wardi. 



Leaves broadly lanceolate, slightly glaucous beneath .7. S. cordata. 



Leaves hairy when fully grown. 



Leaves silvery-silky beneath or on both sides. 



Leaves linear or broadly linear, remotely and minutely serrate 1. S. interior. 



Leaves lanceolate, closely serrate. 



Twigs fragile; leaves tliinly or closely silky on both sides; introduced tree. 



6. S. alba. 



Twigs not fragile; leaves thinly silky beneath; native shrub 8. S. sericea. 



Leaves gray-tomentose, especially beneath. 



Leaves broadly oblanceolate, 5-8 cm. long 9. S. humilis. 



Leaves narrowly oblanceolate, 3-5 cm. long 10. S. tristis. 



1. Salix interior Rowlee. Sandbar willow. 

 Along the upper Potomac. Apr. -May. Eastern N. Amer. {S. longifolia Muhl.) 



2. SalLx nigra Marsh. Black willow. 

 Along streams; common. Apr. -May. Widely distributed in N. Amer. {S. 



nigra falcata Torr.) 



A hybrid between this and S. wardi has been found along the canal near High 

 Island. 



3. Salix wardi Bebb. Ward's willow. 

 Rocky banks and flats along the upper Potomac; common. Apr.-May. Southern 



states, north to Md. {S. nigra wardi Bebb.) 

 The species was described from specimens obtained by Ward near Chain Bridge. 



4. Salix fragilis L. Crack willow. 

 Along the Eastern Branch, Fourmile Run, and Hunting Creek. Apr.-May. 



Native of Eur.; often cultivated and becoming naturalized in eastern N. Amer. 



5. Salix alba L. White willow. 

 Established in a few places along streams. Apr.-May. Native of Eur.; culti- 

 vated or naturalize eastern N. Amer. 



