GENUS I. 



WILLOW FAMILY. 



ii. Populus Sargentii Dode. 



Western Cottonwood. Fig. 



1450. 



P. deltoides occidentalis Rydb. Mem. N. 



Y. Bot. Card, i: 115. 1900. 

 P. Sargentii Dode, Mem. Soc. Hist. Nat. 



Autun 18 : [reprint 40]. 1905. 

 Populus occidentalis Britton ; Tillotson, 



Rep. Board. Agric. Nebr. 1906-7: 218. 



Similar to P. deltoides, the bark 

 thick and gray, the twigs smooth, 

 greenish to light yellow. Leaves 

 glabrous on both sides when mature, 

 broadly triangular-ovate, often wider 

 than long, subcordate to truncate at 

 the base, rather long-acuminate at the 

 apex, the margins coarsely and 

 bluntly toothed; petioles flattened, 

 about as long as the blades ; stami- 

 nate aments 2'-$' long, not very 

 dense ; ripe pistillate aments 5' long 

 or more ; capsules ovoid, $"-j" long, 

 longer than their pedicels. 



River bottoms, Saskatchewan to North 

 Dakota, Nebraska, Kansas and New 

 Mexico. Wood soft and brownish ; 

 weight per cubic foot about 22 Ibs. 

 March-April. 



2. SALIX [Tourn.] L. Sp. PI. 1015. 1753. 



Trees or shrubs, with single-scaled buds, the scales with an adherent membrane within, 

 mostly narrow and short-petioled leaves and persistent or early deciduous broad or minute 

 stipules. Bracts of the aments entire. Disk gland-like, small or minute. Staminate aments 

 dense, erect, spreading or drooping. Staminate flowers with i-io, mostly 2, stamens, their 

 filaments distinct or sometimes united. Pistillate aments usually erect or spreading. Ovary 

 sessile or short-stipitate. Style short or filiform. Stigmas 2, entire or 2-cleft. Capsule mostly 

 2-valved. [Name ancient.] 



About 200 species, of wide geographic distribution throughout the north temperate and arctic 

 zones, a few in the southern hemisphere. Besides the following, some 60 others occur in the northern 

 and western parts of North America. Many hybrids are known. Type species : Salix alba L. 



A. Trees, or large shrubs mostly more than 3 high (no. 24 smaller). 



i. CAPSULE GLABROUS, OR IN NOS. 7 AND 8, SILKY-PUBESCENT, NOT TOMENTOSE. 



Stamens 3-7 (sometimes 2 in no. 6) ; filaments hairy at the base; bracts caducous, light yellow. 

 Pedicels slender, 3-5 times as long as the gland. 

 Petioles and stipules without glands. 

 Leaves green or pale beneath. 



Leaves narrowly lanceolate ; petioles very short. 

 Leaves broadly lanceolate ; petioles slender. 

 Leaves whitish beneath. 

 Petioles and stipules with prominent glands. 

 Summer-fruiting ; leaves green beneath. 

 Autumn-fruiting ; leaves pale beneath. 

 Pedicels about twice as long as the gland. 

 Stamens 2. 



Filaments hairy at the base ; bracts caducous, yellow. 



Pedicels in fruit 1-3 mm. long ; native shrubs or small trees. 

 Leaves entire, finely and almost permanently silky. 

 Leaves denticulate, coarsely silky when young, glabrate in age. 

 Pedicels in fruit less than i mm. long ; large introduced trees. 

 Branches not drooping ; leaves lanceolate. 

 Branches drooping ; leaves linear-lanceolate. 

 Filaments glabrous ; bracts persistent. 

 Mature leaves glabrous. 



Length of leaf-blade less than three times its breadth. 

 Mature leaves thin, dull. 



Mature leaves thick, firm, dark green and shining above. 

 Length of leaf-blade three times its breadth or more. 

 Mature leaves densely silky-pubescent ; capsule subsessile. 



2. CAPSULE TOMENTOSE. 



Filaments united ; capsule sessile ; style none. 

 Filaments distinct. 



1. 5". nigra. 



2. S. amygdaloidcs. 



3. S. Wardi. 



S. lucida. 

 S. serissima. 



6. S.fragilis. 



7. 6". exigua. 



8. S. interior. 



9. S. alba. 



10. S. babylonica. 



11. 5". pyrifolia. 



12. S. glaucophylla. 



13. S. cordata. 



14. 5". adenophylla. 



1 5. S. purpurea. 



