Alder
2 of the 6 encyclopedias on this shelf carry an entry for Alder. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
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.
Collier's New Encyclopedia (1921)
the common name for a genus of plants (alnus), of the order cupiliferæ (oak family). In the eastern United States it is a very common shrub. On the W. coast it often attains a height of from 40 to 60 feet in favorable locations. It is found in temperate and cold regions. The species familiar in England has a wood soft and light, but very durable in the water, and therefore well adapted to mill work, sluices, piles of bridges, etc. Its bark and shoots are used for dye, and its branches for the charcoal employed in making gunpowder.
What Has Changed in the Last Century
Aiton's 1910 description still holds: alders are birch relatives, their wood durable underwater, their bark a tanning and dyeing material. Collier's 1921 filing of the genus Alnus under "Cupuliferae (oak family)" is the one clear error — modern classification puts alders in Betulaceae, the birch family, which Aiton's had already guessed at. Aiton's root "tubercles formed by bacteria" were identified as Frankia, a filamentous actinobacterium quite unlike the rhizobia of clover, which is why alders colonise bare glacial and mining ground so aggressively and are now planted deliberately for that purpose. Newer uses have accumulated rather than replaced the old ones: alder smoke for salmon, and alder bodies for the Fender Stratocaster since the 1950s.
Written for this edition, 2026.