species (Fig. 25a–c). In some species the vessels have spiral thickenings. In
longitudinal sections, they appear somewhat like coiled springs within the
vessels (Fig. 26a–c).
As previously mentioned, ray seriation is a valuable microscopic
feature (Fig. 27a–f ). Also, pitting where ray cells contact the radial walls
of vessels, called ray-vessel pitting, may have a characteristic appearance
(Fig. 28a, b).
Mahoganyfrom the tropical Americas and the West Indies found its
way to Europe through the earliest trade routes. Mahogany is an extremely
variable wood in both color and density and defies simple description.
Heartwood color varies from medium to deep reddish brown. Some wood
is straight grained, but interlocked grain is common, resulting in a ribbon
or stripe figure on radially cut panels. The coarse-textured wood displays
vessel lines on longitudinal surfaces. Growth rings are commonly delin-
eated by terminal parenchyma, visible as fine, creamy light tangential lines
on cross-sectional surfaces and visible among the figured patterns on longi-
tudinal panel surfaces. Seen with a hand lens, the rays are usually conspicu-
ous on transverse surfaces (Fig. 16). A few pores appear to contain chalk-
white inclusions; others have dark contents. The rays of mahogany are
often storied (occurring in a tiered arrangement as viewed on tangential
surfaces), so that ripple marks are produced (Fig. 29). In tangential sections
examined microscopically, the reddish or amber contents of the vessels are
often conspicuous; rays are 1–6 (mostly 3–4) seriate, with relatively large-
diameter cells (Fig. 27b). An important microscopic feature of mahogany
is the extremely minute and numerous intervessel pitting, the individual
pits measuring only 2–3 μmin diameter. This feature serves to separate
mahogany from many other woods that resemble it—Spanish-cedar
(Cedrelaspp.), for example—in which the intervessel pits average 6–8 μm
indiameter.34 Hoadley
a bc
Figure 25a–c
Tangential sections showing examples of
intervessel pitting in hardwoods: (a) large
intervessel pits in poplar (Populussp.);
(b)medium-sized intervessel pits in alder
(Alnussp.); and (c) very small and numerous
intervessel pits in mahogany (Swieteniasp.).
abc
Figure 26a–c
Tangential sections showing examples of spi-
ral thickenings in the vessel elements ofhard-
woods: (a) large-diameter spiral thickenings in
lime (Tiliasp.); (b) fine, evenly spaced spiral
thickenings in maple (Acersp.); and (c) vari-
able diameter and uneven spacing of spiral
thickenings in cherry (Prunussp.).