classified as ring porous. Examples of woods in this category include oak,
chestnut, ash, and elm (Ulmus spp.) (Figs. 11–14). If large earlywood pores
do not form a distinct zone, the wood may be considered semi-ring-porous,
as walnut (Fig. 15). If the pores appear uniform in size and are evenly
distributed throughout the growth ring, the wood is diffuse porous
(Figs.16–23). Tropical hardwoods are commonly diffuse porous, and in
many tropical species the pores are relatively large, as in mahogany. Most
diffuse-porous hardwoods of the temperate regions are fine textured: that
is, the pores are relatively small in diameter, as in maple or poplar.
Although pores are visible with a hand lens, all other cells are too
small in diameter to be seen individually on transverse surfaces. Groups
or masses of cells may, however, be recognized. Masses of denser, thick-
walled fiber cells usually form adarker background mass against which
groups of thinner-walled parenchyma cells produce lighter-colored zones,
lines, or patterns that may be characteristic of a species. For example, the
tangential lines of parenchyma are distinctly visible in mahogany (Fig. 16).
Perpendicular to the growth rings, the rather straight lines of the rays are
also apparent. Rays range in size among hardwoods, from large and con-
spicuous in oak and beech to fine and barely perceptible with a hand lens
on transverse surfaces in poplar and pear.30 Hoadley
Figure 11, right
Oak (Quercussp.), transverse surface.
Figure 12, far right
Chestnut (Castaneasp.), transverse surface.
Figure 13, right
Ash (Fraxinussp.), transverse surface.
Figure 14, far right
Elm (Ulmussp.), transverse surface.
Figure 15
Walnut (Juglanssp.), transverse surface.