Series editors' preface - Wood Tools

56 Conservation of Furniture
(a)
among coniferous species, with a corresponding
diameter range of approximately 20–60 μm
(1 μm = 0.001 mm). The relative diameter of
tracheids is a basis for classifying texture
among conifers. Texture can be estimated by
how clearly individual tracheids can be seen
on a cross-sectional surface with a hand lens,
and is therefore a valuable aid in wood identification.
For example yew (Taxus spp.) is fine
textured, redwood (Sequoia sempervirens) is
coarse textured.
(b)
Figure 2.4 Diagrams of representative cell types
(a) Softwood cell types: Tracheids (A, enlarged view,
A') make up 90–95% of the volume of the wood. The
rest is mainly ray tissue in the form of ray parenchyma
cells (B) or ray tracheids (C). Some species (e.g. larch)
also have a small percentage of epithelial cells (D) that
line the resin canals or longitudinal parenchyma cells
(E). (b) Hardwood cell types: Vessel elements (A) may
vary in shape and size. In hardwoods, tracheids (B)
serve an intermediate function between vessel elements
and fibres. Fibres (C) are long, slender straight cells
that, in comparison to vessel elements, are smaller in
size and have thick cell walls. They impart strength to
the wood. Parenchyma cells, used for transport and
storage, may be longitudinal (D) or radial. They are
similar in cross-section to tracheids, though parenchyma
are shorter. Ray cells may be upright (E) or procumbent
(F)
For a given species, average tangential diameter
of tracheids is fairly consistent. Across a
growth ring, late-wood is distinguished from
early-wood by decreased radial diameter and
increased cell wall thickness. The transition