Elm
2 of the 7 encyclopedias on this shelf carry an entry for Elm. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
a genus of trees, consisting of 13 species, all natives of the N. temperate zone. Two species are common in Great Britain (U. campestris and U. montāná), with many varieties. The U. campestris, or common elm, is a fine tree, of rapid and erect growth, and yielding a tall stem, remarkable for the uniformity of its diameter throughout. The average height of a mature tree is 70 or 80 feet, but some reach 150 feet. The wood is brown, hard, of fine grain, and not apt to crack. The tree generally attains maturity in 70 or 80 years. U. montāna (the mountain or wych elm), a native of Scotland, grows to a less height than the English elm, is of slower growth, and yields a much shorter bole, but it is far bolder in its ramification and more hardy. It usually attains to the weight of about 50 feet. The timber is strong and elastic, and the tree often yields large protuberances of gnarled wood, finely knotted and veined, and much esteemed for veneering. U. glabra, the smooth-leaved elm, is a species common in some parts of Great Britain. The most ornamental tree of the genus is U. pendula, the weeping elm. The American or white elm (U. americana) is abundant in the Western States, attaining its loftiest stature between lat. 42° and 46°; here it reaches the height eight of 100 feet, with a trunk 4 or 5 feet in diameter, rising sometimes 60 or 70 feet before it separates into a few primary limbs. The red or slippery elm (U. fulva) is found over a great extent of country in Canada, Missouri, and as far S. as lat. 31°; it attains the height of 50 or 60 feet, with a trunk 15 or 20 inches in diameter; the wood is of better quality than that of the white elm. The leaves and bark yield an abundant mucilage. The wahoo (U. alata), inhabiting from lat. 37° to Florida, Louisiana, and Arkansas, is a small tree, 30 feet high.
Aiton's Encyclopedia (1910)
a fine spreading tree, belonging to the same family as the nettle, the hop, and the mulberry. There are four elms in the eastern part of the United States . The wahoo elm, a small tree with winged, corky branches, Ohio Valley and southward; the rock elm, of which Oliver Wendell Holmes' parson built his wonderful one-hoss shay; the slippery elm held in fond memory for its delight-yielding inner bark; and the famous American or white elm, the finest shade tree on the continent. The trunk not infrequently attains a girth of sixteen feet. Volumes might be written on the types and individuality of the American elm. It is at once hardy, long-lived, and graceful. The native home of this elm is the rich soil along woodland rivers, but it withstands the trampling of village streets. New England is noted for its elm-lined streets. New Haven is sometimes called the City of Elms . The elm in Cambridge under which Washington took command of the Continental army is called the Washington Elm. Lowell called a volume of his poems, Under the Elms. The flowers have no petals. They come in early spring before the leaves. The fruit of the elm is a flat, circular seed, winged all around with a thin, brown membrane. The ripe fruit flies in the wind like chaff. The leaves are strongly straight-veined. They are short-petioled and are oblique or unequally heart-shaped at the base.