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 em. long, or larger on 
young plants, crenate, rounded, truncate or subcordate at the base: staminate aments 4-6 
em. long, 6-8 mm. thick: stamens about 10: mature pistillate aments 8-10 cm. long, 
about 1 cm. thick : capsules conic, 5-8 mm. long, papillose, 2-valved. 
In dry or moist soil and in thickets, Newfoundland to Alaska, New Jersey, Tennessee and south- 
ward in the Roeky Mountains. 
2. Populus grandidentàta Michx. A forest tree of medium size, occasionally 20-25 
m. high, with a trunk 7 dm. thick. Bark of the trunk irregularly fissured, that on young 
branches smooth and light gray: twigs soon glabrous: winter buds puberulent: leaves 
densely white-tomentose especially beneath when young, early glabrous ; blades ovate, 
6-10 em. 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- 
a "ite 8-12 em. 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 dilatàta 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 Atlantie States. Native of Europe. 
4. Populus deltoides Marsh. A large tree, sometimes 45 meters high, with 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 occidentalis Rydb.; it ranges from Saskatchewan and Alberta south to 
Kansas, Texas and New Mexico. 
. 5. Populus Fremóntii 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 ; 
blades broadly deltoid or reniform-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. 
ur 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 Wislizéni (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 
than 1 dm. long, with pedicels less than 1.5 cm. long: pistillate aments often becoming 1 
dm. long, with slender pedicels nearly 1 em. 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 cándicans Ait. A large tree, reaching a height of 30 m., with 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 em. 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 25-20 m. high, with a maximum trunk diam- 
eter of 1 m., but usually much smaller. Bark reddish brown, flaky: twigs hoary when 
