BOTANY IN RELATION TO STUDY OF TIMBER, 35
may be necessary to take into consideration more minute details,
such as differences in the types of pits on the walls of the various
elements, the presence of gums, and so on. Not infrequently
it is possible to identify a wood on one physical property alone.
SOME ESSENTIAL CHARACTERISTICS OF WOOD.
Colour. Timbers vary enormously in colour. Some, like
species of Dalbergia, are nearly black : this is so in the African
Blackwood (D. Melanoxylon), which is extracted with and
sold as Ebony : the Brazilian Rosewood or Jacaranda (D. nigra)
is also practically black in colour. The heartwood of Lignum-
vitae (Guaiacum) has a very dark colour. The majority of
timbers are some shade of brown, ranging from the dark grey-
brown of most Walnuts (Juglans spp.) to the warm reddish-
brown of Honduras Mahogany (Swietenia macrophylla) and
the pale browns of the Willows (Salix). Many species of Ebony
(Diospyros) are dark brown in colour, usually marked with black
streaks : I am assured by one who has handled a great deal
of this wood that it is rarely the familiar jet-black colour until
it has been treated. Some coniferous woods like Yew (Taxus
baccata) and Pencil Cedar (Juniperus virginiana) have a reddish-
brown colour. Of the more brightly coloured woods there are
the bluish-grey Blue Mahoe (Hibiscus elatus) of tropical America,
which is often used for inlay work, the dull purple Purplehearts
(Peltogyne and Copaifera), and the beautiful reddish Andaman
Padauk (Pterocarpus dalbergioides). Yellow is a colour frequently
encountered : in Box (Buxus), the wood is a pale lemon yellow ;
a slightly darker colour is seen in Haldu (Adina cordifolia), an
Indian timber, while the West African Opepe (Sarcocephalus
esculentus) is a rich orange yellow. A greenish yellow charac-
terises the wood of Greenheart (Nectandra Rodiaei), while woods
of certain Sumachs (Rhus) are of a peculiar dirty yellowish-green
colour. Holly (Ilex) is probably the whitest wood, but other
woods nearly approach it in colour : thus Hornbeam (Carpinus
Betulus) is almost white, while the Western Australian Sandal-
wood (Santalum cygnorum) has a pale cream tint.
Odour. The odour of a wood may be characteristic, and
may affect the value of a wood commercially. Coniferous woods
like Pencil Cedar and Port Orford Cedar (Chamaecyparis
Lawsoniana) have a mild, slightly resinous smell, pleasant to