There are better, longer-lived trees for the open country, but in cities the cottonwood has a use and a message of cheer for rich and poor who look up and learn to know the tree. Unlike the variety next described, the cottonwood takes on dignity with added years.
The Carolina Poplar, considered a variety (Carolinensis) of the cottonwood above, is a strict pyramidal tree of vigorous and surprisingly rapid growth. In cities the varnish on the leaves evidently protects them from dust and smoke. Nurserymen have exploited this tree in America and Europe far beyond its merits, for though useful as a temporary tree, giving shade very soon, poplars should give way gradually to more permanent species planted with them. This poplar soon outgrows the beauty and luxuriance of its youth, and becomes broken and ugly. The immoderate planting of these trees gives a cheap character to many an otherwise handsome town or country place. New summer resorts and city "additions" show poplars in great numbers about their premises. The "poplar habit" is a very short-sighted one and expensive in the long run. J. Wilkinson Elliott, of Pittsburg, persuades his clients to plant Balm of Gilead, a much more satisfactory species.
The Cottonwood (P. Fremontii, Wats.) grows in western California, from Sacramento south, and eastward to Colorado and Texas. It is a favourite shade tree, and an important source of fuel. Cut back systematically, the trees produce abundant crowns of suckers in a very short time.
Fremont's cottonwood is distinguishable from the preceding species by the smaller size of its leaves and the pubescence of its buds. Its laves are sometimes kidney shaped. The bark of old trees is reddish brown. The trees reach loo feet in height.
The Cottonwood (P. Wisliuni, Sarg.) of the Rio Grande Valley in Texas and New Mexico, is a large, wide-crowned tree, with stout, smooth, orange-coloured twigs and leathery, yellow green leaves. Without these distinguishing characters it might easily be confused with the two species last described. The tree is not met with outside its natural range.
Aspen, or Quaking Asp (Populus tremuloides, Michx.)— Slender tree, 4o to 8o feet high, with angular, scarred twigs, and large, vigorous roots. Bark rough, dark on base of trunk, be
coming pale greenish brown or nearly white, and marked with broad, dark bands below the limbs. Wood light brown, sap wood white, soft, close grained, light, weak, not durable. Buds waxy, conical, scaly, brown. Leaves alternate, simple, 1 to 21 inches long, ovate or almost round, with straight base and apex acute; margin faintly toothed; thin, shining green above, dull yellow green beneath; autumn colour yellow; petiole flattened, flexible, slender. Flowers in April, dicecious; catkins pendulous, q to 2i inches long, each flower on notched bract, fringed with hairs; stamens 6 to 12 on disc; ovary conical; stigmas 2-lobed; disc broad, persistent. Fruits, May, borne in drooping aments, 4 inches long; capsules oblong-conical, 2-valved, pale green; seeds oblong, covered with brush of long white hairs. Preferred habitat, sandy or gravelly soil, dry or moist. Distribution, Newfoundland to Hudson Bay and Alaska; south to New Jersey, Pennsylvania, Kentucky, Nebraska; also high altitudes throughout the Rocky Mountains and coast ranges. Uses: Most valuable cover for forest land devastated by fire. Comes up from seed scattered broadcast by wind, and acts as nurse to hardwoods and conifers that later succeed them. A pretty shade and ornamental tree, though short lived.
Aspen is a general term applied to trees of this genus whose leaves have flattened stems. The round-stemmed ones are poplars, proper. The Russian adage: "There is a tree that trembles without even a breath of wind," might well fit this most apprehensive of all the aspen trees. Its dainty round leaf blades twinkle in the sun, a grove of the trees together pro ducing at a little distance the appearance as well as the sound of rippling water. It is the gayest of trees. That was a lugubrious wight who imagined it accursed by being the tree on which Judas Iscariot hanged himself, and doomed "ever afterward to shudder and tremble on account of its connection with the tragedy of Calvary." The same legend attaches to the pretty little redbud, the Judas tree.