Alder

al'der, a genus of trees and shrubs. There are twenty kinds of alder in the northern hemisphere. The most ornamental species is a native of Japan. There are four American alders growing ordinarily from eight to forty feet in height. Alders look very much like willows, but they are closely related to the birches, oaks, and hazels. The surest way to tell an alder from a willow is by the seed. The flat, smooth seeds of an alder are disposed between the scales of egg-shaped or oblong catkins, something after the manner of seeds in pine cones; while the seeds of a willow are clothed with silky down, and are crowded in a pod after the fashion of poplar and cottonwood seeds. Emerson, a close observer of nature, knew the difference well, and wrote:

I thought the sparrow's note from heaven Singing at dawn on the alder bough.

Alder bark is useful in tanning. It furnishes a valuable dye. The English find the wood of the alder durable in water. They employ it for sluices, mill-work, and piling. Like willow, the wood makes valuable charcoal for use in the arts, and especially in the manufacture of gunpowder. The roots of the alder are covered by tubercles formed by bacteria. These colonies of bacteria gather nitrogen, as in the case of clover, and enrich the soil.