wood may contain no rays. In any case, the identification of alder is best
confirmed by microscopic examination of longitudinal tissue sections. In
tangential view, the large rays, if found, are discovered to be aggregate
rays consisting of numerous closely spaced smaller rays (mostly biseriate),
apparently separated by longitudinal cells. The countless other rays
through most of the wood tissue are exclusively uniseriate. Intervessel pits
are relatively small (4–8 μm in diameter), horizontally oval, and spaced
slightly apart from one another (Fig. 25b). Radial sections show ray-vessel
pitting similar to intervessel pitting, and perforation plates are scalariform
with numerous fine bars (Fig. 24a).
The remaining diffuse-porous woods do not have visible features
that faithfully indicate their identity. Hand-lens examination suggests possi-
bilities at best, but final analysis should automatically proceed on the basis
of microscopic features.
Mapleis perhaps the paradigm of diffuse-porous structure. Hand-
lens examination ofend-grain surfaces shows solitary pores or short radial
multiples of pores with very uniform size and distribution. Growth rings
are delineated by a subtle, narrow line of slightly darker tissue, hardly
sufficient to be designated as latewood. Rays appear sharply defined,
appearing approximately as wide as the diameter of the larger pores
(Fig. 19). On tangential panel surfaces, the rays are sometimes not evident,
but on some pieces they may appear as tiny, fine, crowded but distinct
lines; on radial surfaces,a conspicuous ray fleck of darker rays against the
lighter background may be evident, suggesting a beech or plane ray fleck
in miniature. Radial sections showsimple perforations in the vessels. In
tangential sections, intervessel pits appear rather large and distinct, and
rounded or angular through crowding. The vessels show fine, evenly
spaced spiral thickenings (Fig. 26b). In tangential sections the ray cells
appear round. Rays are up to 4 to 5 seriate in the “soft maple” group (e.g.,
Acer campestreand A. platanoides) but up to 8 or more seriate in the “hard-
maple” group (e.g., A. pseudoplatanus).
Cherryheartwood is distinctive in its medium cinnamon-brown
toreddish brown color, which may age to a rather dark brown or reddish
brown. Cherry is relatively fine textured and basically diffuse porous,
although examination ofa transverse surface reveals a concentration of
pores, in some cases suggesting ring-porous arrangement, along the early-
wood edge of the growth ring (Fig. 20). This concentration of earlywood
pores contributes significantlyto the figureof the wood as seen on tangen-
tial panel surfaces. Compared to maple, the pores are less evenly distrib-
uted, with multiples grouped into small clusters, the pores commonly
joined tangentially as well as radially. The rays appear bright and distinct on
cross-sectional surfaces and produce a characteristic light-on-dark ray fleck
on radial panel surfaces ofheartwood. In thin sections examined micro-
scopically, the simple perforation plates and large, distinct intervessel pit-
ting are similar to those of maple. An important difference, however, is in
the spiral thickenings ofthe vessels: in cherry (Fig. 26c) the spirals appear
uneven in thickness and more widely and irregularly spaced than in maple
(F ig. 26b). The widest rays are up to 4 to 5 seriate with rounded cells, as in
maple, but more commonly the rays show uniseriate extensions at either or
both ends. There are many indistinguishably similar species ofPrunus.
Pear(Pyrus spp.) has rather nondistinct visual features, the wood
being very fine textured and uniformly diffuse porous (Fig. 21). In a trans-
verse surface viewed with a hand lens, the pores are barely seen, and soli-36 Hoadley
Figure 29
Tangential surface of mahogany (Swieteniasp.)
showing storied rays resulting in ripple marks.