Insummary, with nothing more than a hand lens, some hard-
woods can be identified at least to the level of their genus by the size and
distribution ofthe pores, the size and distinctiveness of rays, and charac-
teristic patterns of parenchyma cells.
Among the hardwoods, especially the diffuse-porous hardwoods,
microscopic analysis also provides the best means of confirming many
genera and sometimes provides a means ofseparating species within a
genus. Useful features include ray seriation (the width of a ray determined
by a count of the number of cells across the ray as viewed in tangential
section), the type of perforations (openings of the end walls of vessel
cells), the type of intervessel pitting (distinctive patterns of multiple pits
in cell walls connecting vessels laterally), and the presence or absence of
spiral thickenings on the walls of vessels.Ring-porous and semi-ring-porous hardwoods
When end-grain surfaces are examined with a hand lens, four of the hard-
woods presented here stand out as ring-porous woods by virtue of the
conspicuously larger pores forming a distinct row or zone of earlywood
in each growth ring, as is clearly seen in Figures 11–14. Woods with pores
varying gradually in size, from larger earlywood pores to smaller latewood
pores, and without clearly defined earlywood and latewood zones are
classified as semi-ring-porous (synonymous with semi-diffuse-porous)
woods. An example is walnut (Fig. 15). Ring-porous and semi-ring-porous
woods can usually be reliably identified by careful consideration of fea-
tures seen under a hand lens, although it is good practice to verify the
identification by a check of appropriate microscopic features.
In oak(Fig. 11), the regular occurrence of very large rays is the
key feature; they are visible on virtually any surface, forming conspicuous
radial lines across transverse surfaces and visible as distinct lines up to sev-
eralinches long along tangential surfaces. On radial cuts the rays emerge
as irregular but conspicuous patches of contrasting tissue referred to as ray
fleck. Microscopic examination ofa tangential section reveals that the large
conspicuous rays are up to thirty to forty cells wide and thus are multi-
seriate. Among these are the countless narrow rays that are only one cell,
called uniseriate.
In chestnut(Fig. 12), as in oak, the latewood pores occur in irregu-
lar patches that wander radially across the latewood, and these latewood
pores are distinguishable with a hand lens near the earlywood but diminish
to invisibly small and numerous in the outer latewood. But unlike oak,
chestnut lacks any large multiseriate rays, and a microscopic check of a
tangential section reveals that the rays in chestnut are exclusively uniseri-
ate, a feature unique among ring-porous timber of the temperate regions.
Ash(Fig. 13) exhibits a distinct zone of large earlywood pores.
The mass oftissue surrounding the earlywood pores appears lighter than
the denser fiber mass of the latewood. Pores in the first-formed latewood
are solitary or in radial multiples of two or three, with each pore or mul-
tiple surrounded by a narrow band of lighter-colored parenchyma cells. In
the outer latewood, pairs or short strings ofpores often appear to be con-
nected by lighter parenchyma, forming short irregular tangential lines.
As a microscopic check, note that the latewood pores (vessels) are thick
walled, and in European ash (Fraximus excelsior) the rays are commonly
3 and 4 seriate.32 Hoadley