between the other wood cells. They
extend out into the inner bark.

While much may be seen with the unaided eye, better results can be
secured by the use of a good magnifying glass. The end of the wood
should be smoothed off with a very sharp knife; a dull one will
tear and break the cells so that the structure becomes obscured.
With any good hand lens a great many details will then appear which
before were not visible. In the case of some woods like oak, ash,
and chestnut, it will be found that the early wood contains many
comparatively large openings, called _pores_, as shown in Figs. 146
and 147. Pores are cross-sections of vessels which are little
tube-like elements running throughout the tree. The vessels are
water carriers. A wood with its large pores collected into one row
or in a single band is said to be _ring-porous_. Fig. 146 shows such
an arrangement. A wood with its pores scattered throughout the
year's growth instead of collected in a ring is _diffuse-porous_.
Maple, as shown in Fig. 152, is of this character.

[Illustration: FIG. 147.--Example of the Black Oak Group. (Quercus
coccinea.) (Magnified 20 times.)]

All of our broadleaf woods are either ring-porous or diffuse-porous,
though some of them, like the walnut, are nearly half way between
the two groups.

If the wood of hickory, for example, be examined with the magnifying
lens, it will be seen that there are numerous small pores in the
late wood, while running parallel with the annual rings are little
white lines such as are shown in Fig. 149. These are lines of _wood
parenchyma_. Wood parenchyma is found in all woods, arranged
sometimes in tangential lines, sometimes surrounding the pores and
sometimes distributed over the cross-section. The dark, horn-like
portions of hickory and oak are the _woodfibers_. They give the
strength to wood.

In many of the diffuse-porous woods, the pores are too small to be
seen with the unaided eye, and in some cases they are not very
distinct even when viewed with a magnifier. It is necessary to study
such examples closely in order not to confuse them with the woods of
conifers.

The woods of conifers are quite different in structure from
broadleaf woods, though the difference may not always stand out
prominently. Coniferous woods have no pores, their rays are always