Tree

Collier's New Encyclopedia (1921)

in botany, any woody plant rising from the ground, with a trunk, and perennial in duration; an arborescent plant as distinguished from a shrub, an under-shrub, and an herb. The classification of plants which at first suggests itself as the most natural one is into trees, shrubs, and herbs. This is still the popular classification as it was that of the oldest observers (I Kings iv: 33); but it violates all natural affinities, and has long since been abandoned by botanists. Trees occur in many orders, their stems varying in structure according to the sub-kingdoms to which they belong. They may be exogenous, or of that modi fication of the exogenous stem which exists in gymnogens, or may be endogenous or acrogenous. The age of certain trees, especially of exogens, is often great, and, when cut down, the number of years they have existed can be ascertained by counting the annual zones. Some of the giant cedars of California are more than 100 feet in circumference, 400 feet high, and certainly 3,000 years old. Von Martius describes the trunks of certain locust trees in Brazil as being 84 feet in circumference and 60 feet where the boles become cylindrical. From counting the annual rings of one, he formed the opinion that it was of about the age of Homer; another estimate increased the age to 4,104 years, but a third one made the tree first grow up 2,052 years from the publication of Martius' book (1820). A baobab tree (Adansonia digitata) in Senegal was computed by Adanson, A. D. 1794, to be 5,150 years old; but he made his calculations from the measurement of only a fragment of the cross section, and, as zones differ much in breadth, this method of computation involves considerable risk of error. Sir Joseph Hooker rejects the conclusion. Most trees are deciduous, i. e., have deciduous leaves, a few are evergreen. To the latter kind belong those coniferous trees which form so conspicuous a feature in the higher temperate latitudes, while deciduous trees prevail in lower latitudes. The planting of trees is now more attended to than formerly, especially in cities and on the prairie lands of the United States. See FORES- TRY.