GENUS i. 



WILLOW FAMILY. 



587 



Family 5. SALICACEAE Lindl. Nat. Syst. Ed. 2, 186. 1836. 



WILLOW FAMILY. 



Dioecious trees or shrubs with light wood, bitter bark, brittle twigs, alternate 

 stipulate leaves, the stipules often minute and caducous. Flowers of both sexes 

 in aments, solitary in the axil of each bract. Aments expanding before or with 

 the leaves. Staminate aments often pendulous ; staminate flowers consisting of 

 from one to numerous stamens inserted on the receptacle, subtended by a gland- 

 like or cup-shaped disk ; filaments distinct or more or less united ; anthers 2-celled, 

 the sacs longitudinally dehiscent. Pistillate aments pendulous, erect or spreading, 

 sometimes raceme-like; pistillate flowers of a sessile or short-stipitate i-celled 

 ovary subtended by a minute disk ; placentae 2-4, parietal ; ovules usually numer- 

 ous, anatropous ; style short, slender, or almost wanting ; stigmas 2, simple or 2-4- 

 cleft. Fruit an ovoid, oblong or conic 2-4-valved capsule. Seeds small or minute, 

 provided with a dense coma of long, mostly white, silky hairs. Endosperm none. 



The family includes only the 2 following genera, consisting of 200 or more species, mostly 

 natives of the north temperate and arctic zones. 



Bracts fimbriate or incised; stamens numerous; stigmas elongated. i. Po[>ulus. 



Bracts entire; stamens 2-10; stigmas short. 2. Salix. 



i. POPULUS L. Sp. PL 1034. 1753. 



Trees with scaly resinous buds, terete or angled twigs and broad or narrow, usually long- 

 petioled leaves, the stipules minute, fugacious. Bracts of the aments fimbriate or incised. 

 Disk cup-shaped, oblique, lobed or entire. Staminate aments dense, pendulous. Staminate 

 flowers with from 4-60 stamens, their filaments distinct. Pistillate aments sometimes 

 like through the elongation of the pedicels, pendulous,_ erect or spreading. Ovary sessile; 

 style short, stigmas 2-4, entire or 4-lobed. [Name ancient, used for these trees by Pliny.] 

 About 30 species, natives of the northern hemisphere. Besides the following, some 8 others 

 occur in the western parts of North America. Type species: Populus alba L. 



* Petioles terete or channeled, scarcely or not at all flattened laterally. (POPLARS.) 

 Leaves persistently and densely white-tomentose beneath. i. P. alba. 



Leaves glabrous or very nearly so when mature, crenulate. 



Foliage glabrous or nearly so ; capsule very short-pedicelled. 

 Leaves broadly ovate, rounded or cordate at the base. 



Petioles glabrous ; leaves rounded or truncate at the base. 

 Petioles ciliate ; leaves mostly cordate. 



Leaves lanceolate or ovate-lanceolate, mostly narrowed at the base. 

 Leaves acute, short-petioled. 

 Leaves acuminate, long-petioled. 

 Foliage densely tomentose when young ; capsules slender-pedicelled. 



** Petioles strongly flattened laterally. (ASPENS.) 

 Leaves coarsely undulate-dentate. 

 Leaves crenulate-denticulate. 



Leaves ovate or suborbicular, short-pointed. 

 Leaves broadly deltoid, abruptly acuminate. 



Leaves obtuse at the base ; capsules nearly sessile. 

 Leaves truncate at the base ; capsules slender-pedicelled. 

 Pedicels as long as the capsules or longer. 

 Pedicels shorter than the capsules. 



2. P. balsamifera. 



3. P. candicans. 



4. P. angnstifolia. 



5. P. acuminata. 



6. P. heterophylla. 



7. P. grandidentata. 



8. P. trcmnloides. 



9. P. nigra. 



10. P. deltoides. 



11. P. Sargent ii. 



i. Populus alba L. Abele. White or Sil- 

 ver-leaf Poplar. Aspen. Fig. 1440. 



Populus alba L. Sp. PI. 1034. 1753- 



A large tree, with smooth light gray bark, at- 

 taining a maximum height of about 120 and a 

 trunk diameter of 6. Young foliage densely 

 white-tomentose, the leaves becoming glabrate 

 and dark green above, persistently tomentose 

 beneath, broadly ovate or nearly orbicular in out- 

 line, apex acute, base . truncate or ^ subcordate, 

 3-5-lobed or irregularly dentate, 2^-4' long; peti- 

 oles nearly terete, shorter than the blade; stami- 

 nate aments i'-2 r long. 



In yards and along roadsides, springing up froni 

 suckers of older trees. New Brunswick to Ontario 

 and Virginia. Native of Europe and Asia. Wood 

 soft, nearly white; weight 38 Ibs. per cubic foot. 

 Abel or rattler-tree. White or great aspen. Dutch 

 beech. White-bark. March-May. 



