Farther west, covering the mountain slopes from Alaska to Mexico, and liking even better the moist, rich lowlands, is the black cottonwood, the giant of the genus, reaching two hundred feet in height, and seven to eight feet in trunk diameter. Tall and stately, it lifts its broad rounded crown upon heavy upright limbs. In the Yosemite the dark, rich green of these poplar groves along the Merced River makes a rich, velvet margin, glorious when it turns to gold in autumn.
Swamp Cottonwood
P. heterophylla, Linn.
The swamp cottonwood of the South has leaves of variable but distinctly poplar form, always large, broadly ovate, with slim round petioles. The white down of the unfolding leaves often persists into midsummer. On account of the fluttering leaves the trees were called, by the early Acadians, "Langues de femmes" a mild calumny traceable to the herbalist, Gerarde, who compares them to "women's tongues, which seldom cease wagging."
The wood of poplars, soft, weak, and of slight value for fuel or lumber, has within two decades come into a position of great economic importance. Wood pulp is made of it, and out of wood pulp a thousand articles, from toys to wheels of locomotives, are made. A state forester declared: "If I could replace the maples in the state forest by poplars to-day, I would do it gladly. It would be worth thousands of dollars to the state."
THE WILLOWS
Along the watercourses the willow family finds its most congenial habitat. It is a very large family, numbering more than one hundred and seventy species, which are, however, mostly shrubs rather than trees. America has seventy species of willows, and new forms are constantly being discovered, which are the results of the crossing of closely related species. These "natural hybrids" have greatly confused the botany of the willow family.
Not more than half a dozen American willows ever attain the height of good-sized trees, and many of these are more commonly found in the tangled shrubbery of river banks, or covering long semi-arid strips of ground far to the north, or on mountain sides where their growth is stunted. Little trees, six inches high, bearing the characteristic catkins and narrow leaves of the willow, are found on the arctic tundras.
The wood of willows is pale in color, soft in texture, and of very little use as lumber or fuel, except in localities where trees are scarce. The Indian depended upon the inner bark of the withy willow for material for his fish nets and lines, and farmers in the pioneer days took the tough, supple stems, when spring made the sap run freely, for the binding together of the rails of their fences. Knotted tight and seasoned, these twigs hardened and lasted for years.
In Europe the white willow has long been used for the making of wooden shoes, artificial limbs, and carriage bodies. Its wood makes the finest charcoal for gunpowder. Willow wares, such as baskets and wicker furniture, are as old as civilization, and that in its primitive stages. It is a common sight in Europe to see groves of trees from which the long twigs have been taken yearly for these uses. The stumps are called "pollards" and the trees "pollarded willows" whose discouraging task has been to grow a yearly crop of withes for the basket-makers; yet each spring finds them bristling with the new growth.