Exogenous trees are divided into broad-leaved trees and needle-leaved conifers. The broad, flat leaves of trees such as oaks and chestnuts gave rise to the former term, while the narrow resinous leaves of the pine and hemlock gave rise to the latter. The woods of the former group are usually referred to as hard woods, although some of them are very soft; those of the latter group are referred to as soft woods, although some of them are very hard. Most, but not all, of the broadleaf trees are deciduous, that is, they change their foliage every year; and most, but not all, of the needleleaf trees are evergreen, that is, the foliage is persistent. Needleleaf trees are also known as conifers, that is, cone-bearers.
It is usual to associate the terms broadleaf, deciduous, and hard wood; and likewise the terms needleleaf, conifer, evergreen, and soft wood. While generally correct, this is, as seen, not always so. A better division is into broadleaf trees or woods, and needleleaf conifers. [p010]
BROADLEAF WOODS.
The trees affording these woods are found in natural forests and under cultivation in nearly every portion of the globe. The histories of some of them extend back to very remote periods. Their woods were the principal ones in construction until the advent of American soft woods. The oaks, elms, maples, and other so-called hard woods are of this group.
Broadleaf woods are characterized by complex fibre conditions, absence of resins, and greater weights.[11] They are composed of several kinds of cells and fibres, arranged without the regularity so noticeable in the conifers. Cross-sections exhibit numerous, often easily visible pores, arranged in zones or scattered throughout the rings (see plate 2). Pith-rays are numerous and more or less conspicuous, save in softer hard woods such as poplar. Woods are difficult to work in proportion as they are complicated in structure. The numerous members of the group vary from one another and present an extensive range of properties. Trees do not usually afford large pieces. Woods for cabinet work, implements, and other fine purposes are from this group. The total requirement is less than for needleleaf woods.
The leaves of broadleaf trees are easily distinguished from the resinous, usually evergreen ones of the conifers. Most of them are deciduous, that is, shed every season, although some are persistent, that is, "evergreen." "Broadleaf," "deciduous," and "hardwood" trees are the same. [p011]
FOOTNOTES
[9] Circular No. 16, U. S. Forestry Division.
[10] Some woods, as birdseye maple, are well developed by the rotary cut. A revolving log is advanced against a tool which pares a broad thin ribbon suitable for veneered work.
[11] Neither resin-ducts nor resin exists in these woods, save sometimes in buds and leaves.