490 



SALICACEAE. 



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 con- 

 sisting 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 numerous, anatropous; style short, slender, or almost wanting; 

 stigmas 2, simple or 2-4-cleft. Fruit an ovoid, oblong or conic 2-4-valved cap- 

 sule. Seeds small or minute, provided with a dense coma of long, mostly white, 

 silky hairs. Endosperm none. Cotyledons plano-convex. Radicle short. 



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. Populus. 



Bracts entire ; stamens 2-10; stigmas short. 2. Sali.v. 



i. POPULUS L. Sp. PI. 1034. 1753. 



Trees with scaly resinous buds, terete or angled twigs aud 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 

 raceme-like through the elongation of the pedicels, pendulous, erect or spreading. Ovary 

 sessile; style short, stigmas 2-4, entire or 4-lobed. Capsule 2-4-valved. Coma of the seeds 

 often very long and conspicuous. [Name ancient, used for these trees by Pliny.] 



About 25 species, natives of the northern hemisphere. Besides the following, some 3 others 

 occur in the western parts of North America. 



%. 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 strictly glabrous (except in P. balsamifera candicans); capsule very short-pedicelled. 



Leaves broadly ovate, rounded or cordate at the base. 



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



Leaves acute, short-petioled. 



Leaves acuminate, long-petioled. 

 Foliage densely tomentose when young; capsiiles 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. 



2. P. balsamifera. 



3. P. angustifolia. 



4. P. acuminata. 



5. P. heterophylla. 



6. P. grandidentata. 

 ~. P. tremuloides. 



8. P. nigra. 



9. P. deltoides. 



i. Populus alba L,. Abele. White or 

 Silver-leaf Poplar. (Fig. 1164.) 



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 

 outline, apex acute, base truncate or subcordate, 

 3~5-lobed or irregularly dentate, 2> / -4 / long; 

 petioles nearly terete, shorter than the blade; 

 staminate aments I'-a' long. 



In yards and along roadsides, springing up from 

 suckers of older trees. New Brunswick to Virginia. 

 Native of Europe arid Asia. Wood soft, nearly 

 white; weight 38 Ibs. per cubic foot. March-May. 



