SALICACEAE 339 



of young leaves. Bark rather smooth : leaves numerous, very restless on account of the 

 slender elongated petioles ; blades ovate or orbicular-ovate, 3-8 cm. long, or larger on 

 young plants, crenate, rounded, truncate or subcordate at the base : staminate aments 4-6 

 cm. long, 6-8 mm. thick: stamens about 10: mature pistillate aments 8-10 cm. long, 

 about 1 cm. thick : capsules conic, 5-8 ram. long, papillose, 2-valved. 



In dry or moist soil and in tliickets, Newfoundland to Alaska, New Jersey, Tennessee and south- 

 ward in the Rocky Mountains. 



2. Populus grandldentata Michx. A forest tree of medium size, occasionally 20-25 

 ra. high, with a trunk 7 dm. thick. Bark of the trunk irregularly fissured, that on young 

 branches smootli and light gray : twigs soon glabrous : winter buds puberulent : leaves 

 densely white-tomentose especially beneath when young, early glabrous ; blades ovate, 

 6-10 cm. long, or 3 dm. long on young plants, short-acuminate, coarsely dentate, obtuse 

 or truncate at the base ; petioles laterally flattened, 4-6 cm. long ; stipules linear, 1 cm. 

 long: staminate aments 4-10 cm. long, about 1 cm. thick: stamens 6-12 : mature pistil- 

 late aments 8-12 cm. in length, somewhat pubescent: capsules conic, 4-7 mm. long, 2- 

 valved. 



On dry uplands and in rich woods, Nova Scotia and Ontario to Minnesota, New Jersey and along 

 the mountains to North Carolina and Tennessee. 



3. Populus dilatata Ait. An ornamental tree of very rapid growth, with a fastigiate 

 top. Buds very resinous : leaves stiff ; blades deltoid or subrhomboid, crenate, or crenate- 

 serrate, short-acuminate, glabrous, firm, slender-petioled : staminate aments 2-5 cm. long, 

 cylindric, densely flowered: stamens 6-8 ; anthers purple : pistillate aments about as long 

 as the staminate. 



In fields and pastures, and about gardens, naturalized in the Atlantic States. Native of Europe. 



4. Populus deltoides Marsh. A large tree, sometimes 45 meters high, Avith a trunk 

 2-3 meters in diameter, the foliage glabrous. Bark of trunk gray, deeply divided into inter- 

 rupted longitudinal ridges in age : twigs olive-green, stout : winter buds resinous, ovoid, 

 acute, 2 cm. long, with 7-8 brown scales : leaves numerous ; blades broadly ovate to deltoid, 

 abruptly acute or acuminate, coarsely serrate or crenate-serrate, truncate at the base ; 

 petioles as long as the blades or shorter : staminate aments short-peduncled, 8-12 cm. long, 

 10-12 mm. thick : mature pistillate aments 20-30 cm. long ; bracts scarious : stamens 60 or 

 more : capsules ovoid, 8-10 mm. long, acute, 2-4-valved, as long as the pedicels or shorter. 



In moist soil, common along streams, Quebec to Manitoba, Florida and Tennessee.— A campestrian 

 variety, with light yellow shining branches, broader leaf-blades with longer acuminations and coarser 

 teeth 'is known as P. deltoides occidentiUis Rydb.; it ranges from Saskatchewan and Alberta south to 

 Kansas, Texas and New Mexico. 



5. Populus Fremontii S. Wats. A large tree, reaching a height of 30 m. and a max- 

 imum trunk diameter of about 2 m. Bark gray, more or less fissured : leaves numerous ; 

 lilades broadly deltoid or reniforni-deltoid, 6-12 cm. broad, with rather numerous, rela- 

 tively fine crenate teeth, abruptly contracted into the slender petioles : aments raceme-like : 

 the staminate 7-12 cm. long, with pedicels 1.5-2 cm. long: pistillate aments 8-11 cm. 

 long at maturity, copiously fruiting: capsules ovoid, 8-12 mm. long, often with 3 leathery 

 valves. 



On river banks, Colorado to California, Texas, Mexico and Lower California. 



6. Populus Wisliz^ni (S. Wats. ) Small. A tree, resembling P. Fremontii, but of 

 more southern range. Bark cracked, often light gray : leaves numerous ; blades deltoid 

 or somewhat reniform, mostly less than 1 dm. broad, usually with abrupt entire acumina- 

 tions and few relatively coarse crenate teeth, more or less cuneately -narrowed into the slen- 

 der petioles from a broad rather truncate base : aments raceme-like : staminate mostly less 

 tlian 1 dm. long, with pedicels less than 1.5 cm. long : pistillate aments often becoming 1 

 dm. long, with slender pedicels nearly 1 cm. long : capsules ovoid, fully 1 cm. long, usu- 

 ally 4-angled and 4-valved. 



Along streams, southern Texas and the Rio Grande Valley. 



7. Populus candicans Ait. A large tree, reaching a height of 30 m., wath a maxi- 

 mum trunk diameter of about 2 m., with spreading branches and scantily pubescent, very 

 resinous fragrant buds. Leaves quite fleshy ; blades broadly ovate, cordate, nearly or 

 quite glabrous, 6-15 cm. long, dark green above, pale beneath, except the margins and 

 nerves, coarsely crenate with gland-tipped teeth : petioles generally pubescent : aments 

 preceding the leaves : staminate 8-14 cm. long, fully 1 cm. thick : stamens 18-30 : mature 

 pistillate aments 10-15 cm. long, lax, much interrupted : stigmas with dilated lobes : cap- 

 sules conic or ovoid, 8-11 mm. long, short-pedicelled, 2-valved. 



In moist or dry soil, mostly escaped from cultivation, New Brunswick to Minnesota and Georgia. 



8. Populus heterophylla L. A tree 25-30 m. high, with a maximum trunk diam- 

 eter of 1 m., but usually much smaller. Bark reddish brown, flaky: twigs hoary when 



