Aspen (_Populus tremuloides_).—Commonly called quaking aspen. Flat,
broadly oval leaves, up to 4½ inches across, that tremble
characteristically in a breeze. Bark whitish or very pale green,
smooth, with black scars where branches have dropped off. Trees
rarely more than 60 feet high.
Narrowleaf cottonwood (_Populus angustifolia_).—Usually a tall tree, 40
to 60 feet high. Bark light yellow-green, divided near the base of
old trees into flat ridges; smooth and thinner above. Leaves ¼ to
1 inch wide and 2 or 3 inches long, very similar to willow leaves.
Usually found along streams at lower elevations.
Mountain alder (_Alnus tenuifolia_).—Found along and overhanging
streams, usually in clumps, several trees growing from the same
root, frequently 4 to 6 inches in diameter and 15 to 25 feet high.
Leaves double-toothed, 2 to 4 inches long and 1½ to 2½ inches
wide. Mature seed-bearing fruit noticeable in winter.
Willows (_Salix, sp._).—The common shrub of creek bottoms. Usually
narrow, sharp-pointed leaves. Some willows attain a diameter of 4
inches and a height of 15 to 25 feet. Buds are covered by a single
scale.
Western choke cherry (_Prunus demissa_).—Clustered flowers and fruit;
alternate leaves, sharply pointed. Bark, leaves, and seed bitter.
Fruit black. Tree, or more often a shrub, up to 15 feet in height.
Scrub oak (_Quercus sp._).—Usually a shrub, rarely over 15 feet high.
Alternate leaves, smaller at the base than at the ends, with deep
lobes, frequently drying on the tree and remaining over winter.
Fruit, a short pointed acorn. Forms dense thickets at lower
elevations. Often valuable for fence posts.
Pacific serviceberry (_Amelanchier florida_).—Leaves silvery, sharply
toothed above the middle and alternate on branches. Trees, or more
often shrubs, 6 to 15 feet high. Flowers white and in clusters.
Five hard seeds in each berry. Berries edible, nearly black, when
ripe.
Rocky Mountain maple (_Acer glabrum_).—Usually a shrub, but frequently
20 to 30 feet high. Paired opposite buds, 3 to 5 lobed leaves,
dark reddish-brown bark, and paired, winged seed. Leaves 3 to 5
inches in diameter, opposite each other.
Boxelder (_Acer negundo_).—Compound leaves with 3 to 5, rarely 7,
leaflets, pale-gray or light-brown bark, and paired, winged seeds,
which ripen in the autumn. Compound leaves opposite each other.
Hawthorn (_Crataegus sp._).—Usually a shrub; dark scaly bark; leaves
simple and alternate; fruit small, fleshy, and in clusters. Armed
with sharp spines.
_Six Rules for Health Protection_
1. PURIFICATION.—Mountain streams will not purify themselves in a few
hundred feet. Boil or chlorinate all suspected water.