BOTANY IN RELATION TO STUDY OF TIMBER. 37
the other hand a piece of Borneo Camphor wood, which came
into my possession less than a year ago, has lost its characteristic
smell, and this is not restored by sandpapering. Similarly, a
piece of Queensland Walnut, which a year ago had a most
unpleasant smell, is now odourless. Woods like Uganda Green-
heart and Cigar-box Cedar seem to retain their smell indefinitely
without the intervention of sandpaper.
Surface. The surface of a wood sometimes produces a
characteristic sensation to the sense of touch. Lignum-Vitae
has a surface which feels waxy, Teak often feels greasy. In
general a wood of light weight feels warm, a feature particularly
noticeable in Alder (Alnus glutinosa), which, for this reason,
among others, is used for making clogs : heavy woods usually
feel cold ; this is particularly apparent in Hornbeam.
Taste. A few timbers have a characteristic taste. The
Partridge Wood (Andira inermis), and Quassia Wood (Quassia
amara), both tropical American woods, have a bitter taste
if chewed, leaving a taste like quinine in the mouth. Oak
has an astringent taste, doubtless owing to the abundance
of tannin it contains. Logwood (Haematoxylon campechianum)
has a sweetish taste, while Goupia has an unpleasant taste which
Stone describes as nauseous : the taste is not very marked in
the dry wood.
Extracts. A characteristic feature of a few woods is that
of yielding a fluorescent aqueous extract. This is well seen
in woods of the genus Pterocarpus, especially in the Red Sanders
Wood (P. santalinus), in which the watery extract is yellow
by transmitted light and blue by reflected light.
THE STRUCTURE OF WOOD.
A general account of the structure of wood can be obtained
from any good botanical textbook, and will only be dealt with
here in the most general terms.
If the end of a log of Oak be examined it will be found to con-
sist of numerous concentric circles, the annual rings, while radiat-
ing from the central stellate pith, or at least from some point on a
radius, are silvery streaks, the rays. The centre of the log is a
warm brown colour, and is termed the heartwood, while a zone at
the periphery is paler and is known as the sapwood. The rays,
which are used largely for the storage of elaborated food materials,