Coniferae

Coniferae, the most numerous order of gymnosperms, including several hundred species of trees and shrubs, comprised in some 35 genera. They have generally a tap root; an exogenous stem of tapering form, branching freely in pseudo-whorls; leaves reduced to rigid needles, mostly evergreen; and unisexual, wind-pollinated flowers, the female ones forming a seed-bearing cone (q.v.), The wood, which often forms wide annual rings, has inconspicuous medullary rays, and consists mainly of tracheides with bordered pits. The leaves are broad in Gingko and Araucaria; deciduous in Taxodium and the larches; in whorls of three in juniper; and in clusters of two, three, or five, in the axil of a membranous scale-leaf in the pines. With the exception of the yew (Taxus) conifers abound in resin-passages both in their stems and in their leaves. There being no perianth or closed ovary, the ovules are naked, and the pollen-grain falls directly into the micropyle. The seeds are filled with archisperm, formed before fertilisation, and the cotyledons are often green before germination and deeply lobed, so that the order has been termed "polycotyledonous." Some species reach a large size, Sequoia gigantea, the Mammoth tree of California, attaining 450 ft. in height, with a diameter of 37 ft. at the base. Many kinds are valued as ornamental trees, and others yield turpentine, resin, pitch, oil, and timber.