ASPEN, trees of the family Salicacetr and genus Populus, native of the cooler parts of Europe and Asia, and best upon moist, gravelly soils. They grow quickly; usually attain a height of 50 to 60 feet, some times even 100 feet; have light, small, thin, toothed leaf-blades upon long, slender, flat tened petioles which permit the blade to flutter with the least breeze, hence the specific name of the European aspen, P. tremula, qremulous.x' The wood being white, light, soft, and porous, is not a valuable fuel, but is useful for making charcoal for the manufacture of gunpowder, and for turning, often being employed for making bowls, trays, troughs, and pails. The wood may be made harder and thus rendered useful for interior work in houses by peeling off the bark and allowing the stem to dry be fore felling it. In places where this tree abounds, and other timber is scarce or expen sive, this method of hardening is very useful. The bark is rich in glucoside called salicin and used in leather tanning. In the United States the European tree is best known as an ornamental one, its variety, pendula, with graceful, drooping branches, being per haps the best weeping poplar. The male
plants are preferred because of the abundance of their catkins which appear in early spring before the catkins of American species blos som. The American aspen (Populus trems loides), very generally distributed from Alaska to Labrador and southward to Pennsylvania and California, and in the mountains to Mex ico, closely resembles the preceding species. Its light-gray branches render it conspicuous in clearings where it is one of the first trees to appear. It is said to attain a height of 100 feet when grown in the forest, but is usually much smaller. This tree, like the following, is widely used in the manufacture of wood pulp. The large-toothed aspen (Populus grandiden tato) is a large American species found from Nova Scotia to Minnesota and southward to Tennessee. See POPLAR.