40 OF WOOD IN GENERAL 



Among minor characters sometimes of use in discriminating 

 woods may be mentioned the colour of a solution obtained by 

 boiling the wood in water or in alcohol, its reaction when treated 

 with a solution of iron sulphate or perchloride, and the colour ot 

 the ash produced in burning. Jarrah, for instance, yields a black 

 cindery mass, whilst the only less valuable paving wood Karri 

 gives a white ash. 



Unfortunately trees of the same Order, or even of the same 

 genus, by no means always have similar woods. Mr. Gamble, for 

 instance, cites the important genus Dalbergia, three Indian species 

 of which— the Blackwood (D. latifoUa), Sissoo (D. Sissoo), and D. 

 lanceoldria—heiYe hard, dark-coloured, heavy woods ; whilst other 

 species have only white and dften soft sapwood, not forming any 



Fig. 29.— Transverse section of Linden, a ring-porous wood, showing three annual 

 rings. (After Van Tieghem, from The Mements of Botany, "by permission of Mr. 

 Francis Darwin and the Syndicate of the Cambridge University Press.) 



' duramen,' or heartwood. When, however, we compare heartwoods 

 microscopically they do as a rule resemble one another in allied 

 species. 



In many eases a knowledge of the locality from which a timber 

 comes may aid us in identifying it. Thus, save by this means, it 

 is apparently impossible to distinguish the woods of Cupressus 

 LawsonidTia from Oregon, G, thyoides from the Eastern States, 

 Th'^ya gigdntm, the Canoe Cedar or Red Cedar of the West, and 

 T, occidentalism the Arbor- vitse of the North-east, aU of them being 

 known to American timber-merchants as White Cedar. 



The following table is by no means exhaustive, few Asiatic or 

 Australian woods being, as yet, classified in it. It has seldom 

 been possible to carry the discrimination further than genera. 

 Though obvious naked-eye characters have been largely employed^ 

 use is also made of those seen only in microscopic sections. For 



