SILVA OF NORTH AMERICA. SALICACEZ. 
172 
by a short or elongated style and two oblique dilated irregularly lobed stigmas deciduous from the fruit, 
and inclosed at the base in a shallow cup-shaped disk shghtly and irregularly lobed on the margins 
and raised on a short pedicel. The pistillate ament lengthens as the capsules enlarge, and when they 
open in May or early in June it is from two and a half to four inches in length, with pedicels often a 
third of an inch long; the capsule is broadly ovate, often rather abruptly contracted above the middle, 
short-pointed, rugose, thin-walled, two-valved, and surrounded at the base by the membranaceous disk 
of the flower. The seeds are ovate or obovate, rather acute, light brown, nearly an eighth of an inch 
long, and surrounded by long soft lustrous white hairs. 
Populus angustifolia inhabits the banks of streams usually at elevations of from five to ten 
thousand feet above the level of the sea, and is distributed from the valley of the Milk, Belly, and 
other streams in southwestern Assiniboia,' the Black Hills of Dakota® and northwestern Nebraska,’ 
southward through the mountain regions of the interior of the continent, to the ranges of central 
Nevada, the Mogollon Mountains of New Mexico,’ and the ranges of central Arizona,® and is the 
common Poplar of northern Colorado, Utah, Wyoming, southern Montana, and eastern Idaho.° 
The wood of Populus angustifolia is light, soft, and weak; it contains numerous obscure 
medullary rays and minute scattered open ducts, and is light brown, with thin nearly white sapwood 
composed of from ten to thirty iayers of annual growth. The specific gravity of the absolutely dry 
wood is 0.3912, a cubic foot weighing 24.38 pounds. 
The earliest description of the Narrow-leaved Cottonwood appears in the narrative of the expedi- 
tion which crossed the continent under command of Captains Lewis and Clark in 1804-1806,’ but the 
name was not published until several years later, when it was found in Colorado by Dr. Edwin James,’ 
the surgeon and naturalist of the party sent by the government of the United States, under command 
of Major Long, to explore the southern Rocky Mountains. 
Populus angustifolia, which in habit and in the shape and color of its leaves resembles some of 
the broad-leaved Willows, is very generally planted as a shade-tree in the streets of the towns of 
Colorado and Utah, where it grows rapidly when well supplied with water, and soon forms a shapely 
conical head. It is occasionally cultivated in the gardens of the United States and Europe, and has 
proved hardy in eastern Massachusetts, where it is established in the Arnold Arboretum. 
1 Macoun, Cat. Can. Pl. 457. 
2 Williams, Bull. No. 43, South Dakota Agric. Coll. 104. 
3 Bessey, Rep. Nebraska State Board Agric. 1894, 104. 
# Rusby, Bull. Torrey Bot. Club, ix. 106. 
5 The specimen (No. 2990) without flowers or fruit of a Poplar 
collected by Mr. S. B. Parish in June, 1894, in Rattlesnake Cafion, 
at an elevation of 5,500 feet at the eastern base of the San Bernar- 
dino Mountains in California, preserved in the National Herbarium, 
is probably of this species, although I have no other evidence that 
it crosses the California deserts (S. B. Parish, Erythea, iii. 60). 
® A Poplar (Populus acuminata, Rydberg, Bull. Torrey Bot. Club, 
xx. 46, t. 149 [1893]) with rhomboidal leaves rather coarsely serrate 
at the middle only and long petioles, described as a large tree with 
a broad pyramidal crown of spreading branches, is distributed from 
the Black Hills of South Dakota and western Nebraska to the east- 
ern base of the Rocky Mountains in Colorado, and apparently also 
occurs in Mexico ; although often confounded with Populus angus- 
iifolia, it is probably a distinct species, and will be included in a 
supplement to The Silva if sufficient material can be obtained from 
which to prepare a plate and description. 
7 On June 6, 1805, the party was on the Tansy (now Teton) 
River, a tributary of the upper Missouri, where they found “a 
species of Cottonwood, with a leaf like that of the Wild Cherry,” 
and on the 12th of June they noticed that “with the broad-leaved 
Cottonwood, which has formed the principal timber of the Mis- 
souri, is here mixed another species, differing from the first only in 
the narrowness of its leaf and the greater thickness of its bark. 
This species seems to be preferred by the beavers to the broad- 
leaved, probably because the former affords a deeper and softer 
bark.” (See A History of the Expedition under Command of Lewis 
and Clark, ed. Coues, ii. 356, 364.) 
8 See ii. 96. 
