ence is so great that in a study of wood structure it is
best to consider the two kinds separately.

In this country the great variety of woods, and especially of useful
woods, often makes the mere distinction of the kind or species of tree
most difficult. Thus there are at least eight pines of the thirty-five
native ones in the market, some of which so closely resemble each
other in their minute structure that one can hardly tell them apart,
and yet they differ in quality and are often mixed or confounded in
the trade. Of the thirty-six oaks, of which probably not less than six
or eight are marketed, we can readily recognize by means of their
minute anatomy at least two tribes--the white and black oaks. The same
is true of the eleven kinds of hickory, the six kinds of ash, etc.,
etc.

The list of names of all trees indigenous to the United States, as
enumerated by the United States Forest Service, is 495 in number, the
designation of "tree" being applied to all woody plants which produce
naturally in their native habitat one main, erect stem, bearing a
definite crown, no matter what size they attain.

Timber is produced only by the Spermatophyta, or seed-bearing plants,
which are subdivided into the Gymnosperms (conifers), and Angiosperms
(broad-leaved). The conifer or cone-bearing tree, to which belong the
pines, larches, and firs, is one of the three natural orders of
Gymnosperms. These are generally classed as "softwoods," and are more
extensively scattered and more generally used than any other class of
timber, and are simple and regular in structure. The so-called
"hardwoods" are "Dicotyledons" or broad-leaved trees, a subdivision of
the Angiosperms. They are generally of slower growth, and produce
harder timber than the conifers, but not necessarily so. Basswood,
poplar, sycamore, and some of the gums, though classed with the
hardwoods, are not nearly as hard as some of the pines.

SECTION II

CONIFEROUS TREES

WOOD OF THE CONIFEROUS TREES

Examining a smooth cross-section or end face of a well-grown log of
Georgia pine, we distinguish an envelope of reddish, scaly bark, a
small, whitish pith at the center, and between these the wood in a
great number of concentric rings.

Bark and Pith

The bark of a pine stem is thickest and roughest near the base,
decreases rapidly in thickness from o