Series editors' preface - Wood Tools

the United States. In the UK, the Timber
Research and Development Association
(TRADA) has published simple keys of this
type for both hardwood and softwood identification.
Dichotomous identification keys,
accompanied with 10 to 15 photographs of
transverse cross-sections of wood provide useful
supportive data with the hand-lens identification
method (Normand, 1972). The main
disadvantage of this approach is that no match
will be found when that particular genus or
species is not included in the key, means that
it is often useful to adopt a more flexible
approach (Brazier and Franklin, 1961; Hoadley,
1990).
Multiple entry key systems exist that are
based on either perforated cards or computer
systems. Examples of multiple entry perforated
card systems are published by the Forest
Products Research Laboratory (FPRL) and
described by Brazier and Franklin (1961),
Phillips (1960) and Henderson (1960). Multientry
computer sorting systems have been
developed based on the traditional FPRL perforated
card system. Especially within the
International Association of Wood Anatomists
(IAWA), there is an ongoing discussion about
some of these programs, combined with
reviews of suitable wood anatomical features.
The General Unknown Entry Search System
(GUESS) by Wheeler (Wheeler et al., 1986) is a
useful and inexpensive PC program containing
more than five thousand taxa in eight different
databases, and is accompanied by an excellent
textbook. Miller (1980), and Miller et al. (1981,
1987) has described more elaborate systems
that operate with a larger number of features.
Other programs were developed for specific
regions or countries. Jiaju and Fang (1990)
describe the Wood Identification Program
(WIP) for woods mostly from China. A review
of current computer search programs is given
by Wheeler and Baas (1998).
Reference material should consist of microscope
slides made of vouchered wood
samples, wood descriptions and photo-micrographs
of wood sections (Détienne and
Jacquet, 1983; Fahn et al., 1986; Grosser, 1977;
Miles, 1978; Panshin and deZeeuw, 1980;
Schweingruber, 1990). Vouchered wood samples
are specimens of woody plants of which
the leaves, fruits or flowers also were collected
of the same exact plant, and identified to the
Wood and wooden structures 61
species level for taxonomic purposes. Gregory
(1980) provides an annotated bibliography on
wood identification including a listing by
botanical family, growth regions and microscopic
features with cross references to more
than 450 bibliographic entries.
Wood identification is typically an invasive
and destructive process, at least to the extent
that some wood tissue must be disturbed. The
process usually consists of removing small
samples or sections, or at least in cleanly cutting
into a surface to expose cell structure for
examination. In identifying woods of historic
objects, a primary responsibility is to utilize
approaches that accomplish identification with
the least possible disturbance to the object.
2.2.5 Hand–lens examination
A routine starting point in identifying a given
piece of wood is to locate a tiny area of endgrain
surface where the wood can be cut
cleanly with a razor blade or equally sharp tool
to expose longitudinal cells in cross-section.
When the exposed surface is examined with a
good quality 10 magnifier or hand lens, it can
immediately be identified as a hardwood
(pores visible) or softwood (pores absent). In
addition, placement of growth rings and rays
indicates the orientation of radial and tangential
planes in the wood.
In cases where pores (and in some cases
conspicuous rays) give immediate indication
that the unknown is a hardwood, the pore distribution
and size range suggests whether the
wood is ring-porous, semi-ring-porous or diffuse-porous.
This process of examination and
deduction continues until all features have
been evaluated. In summary, among hardwoods,
hand lens observation of transverse
surfaces reveals the relative width and distinctiveness
of rays, the size and distribution of
pores, and characteristic patterns of parenchyma
cells.
An acetate measuring gauge, which can be
ordered from most forest products laboratories,
is helpful in measuring features such as pore
quantity and size. Careful evaluation of typical
characteristics will usually suggest an identification,
at least to the genus, for most temperate
region hardwoods. However, it is routinely
recommended to follow through with microscopic
examination of thin sections to confirm