ear the stump, and decreases
upward in the stem, thus fully accounting for the difference in weight
and firmness of the wood of these different parts.

[Illustration: Fig. 1. Board of Pine. CS, cross-section; RS,
radial section; TS, tangential section; _sw_, summer-wood;
_spw_, spring-wood.]

In the long-leaf pine the summer-wood often forms scarcely ten per
cent of the wood in the central five rings; forty to fifty per cent of
the next one hundred rings, about thirty per cent of the next fifty,
and only about twenty per cent in the fifty rings next to the bark. It
averages forty-five per cent of the wood of the stump and only
twenty-four per cent of that of the top.

Sawing the log into boards, the yearly rings are represented on the
board faces of the middle board (radial sections) by narrow parallel
strips (see Fig. 1), an inner, lighter stripe and its outer, darker
neighbor always corresponding to one annual ring.

On the faces of the boards nearest the slab (tangential or bastard
boards) the several years' growth should also appear as parallel, but
much broader stripes. This they do if the log is short and very
perfect. Usually a variety of pleasing patterns is displayed on the
boards, depending on the position of the saw cut and on the regularity
of growth of the log (see Fig. 1). Where the cut passes through a
prominence (bump or crook) of the log, irregular, concentric circlets
and ovals are produced, and on almost all tangent boards arrow or
V-shaped forms occur.

Anatomical Structure

Holding a well-smoothed disk or cross-section one-eighth inch thick
toward the light, it is readily seen that pine wood is a very porous
structure. If viewed with a strong magnifier, the little tubes,
especially in the spring-wood of the rings, are easily distinguished,
and their arrangement in regular, straight, radial rows is apparent.

[Illustration: Fig. 2. Wood of Spruce. 1, natural size; 2,
small part of one ring magnified 100 times. The vertical
tubes are wood fibres, in this case all "tracheids." _m_,
medullary or pith ray; _n_, transverse tracheids of ray; _a_,
_b_, and _c_, bordered pits of the tracheids, more enlarged.]

Scattered through the summer-wood portion of the rings, numerous
irregular grayish dots (the resin ducts) disturb the uniformity and
regularity of the structure. Magnified one hundred times, a piece of
spruce, which is similar to pine