Both transmission electron microscopy and scanning electron microscopy (SEM) are useful in examining features (such as vestured pits) that may otherwise be difficult to observe.
SEMs equipped with an Energy Dispersive X-ray Spectrometry (EDS) system can be helpful in analysing wood inclusions such as naturally occurring calcium deposits (Core et al., 1979). Blanchette et al. (1992b) used TEM and SEM-EDS to determine the source of the green coloration of decorative furniture woods. This showed that colour was due to the presence of the hyphae of Chlorociboria and associated coloured deposits rather than copper stains.
When only a tiny fragment of wood is available, too small to be sectioned, it may be practical to make a maceration. A mixture of glacial acetic acid and hydrogen peroxide (Franklin's method) can be used to break down the wood into individual cell-elements. These elements are then mounted and examined (Jane, 1970; Panshin and deZeeuw, 1980).
Dyer (1988), Avella et al. (1988) and Hoadley (1990) have shown that some wood species display autofluorescence examined by long wave UV light. The ideal opportunity for observing autofluorescence of wood is to examine the fresh surface where a sample for wood identification has been taken.
Chemical spot tests sometimes can provide additional information in differentiating wood species. Chrome azurol, for example, will turn bluish when brought in contact with species containing elevated levels of aluminium (Kukachka and Miller, 1980). Chemical methods for discriminating between the heartwood of red and white oak and between red maple and sugar maple are described by Panshin and deZeeuw (1980).
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