DISTINCTIVE CHARACTERS. 47 



the pores are in short, wavy lines, and there are wavy false rings ; 

 but whilst the Ebendcece have white, grey or black wood, that of 

 the Sapotdcece is reddish. So too the tropical Order Anondcecr, 

 or Custard-Apple family, which includes the Lancewood of the 

 West Indies, has regular ladder-like transverse bars on its woods 

 that are very characteristic. 



Several of the characters used in the classification of woods, 

 such as weight per cubic foot, hardness and amount of ash left on 

 combustion, not only vary together, but also differ according to 

 the age of the tree and the distance of the sample from the root. 

 Weight, for instance, increases from the butt to the lowest branch, 

 and decreases from the latter point upward. 



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 of 

 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 Dalbtrgia, three Indian species 

 of which the Blackwood (D. latifllia), Sissoo (D. Sissoo), and D. 

 lanceoldria have hard, dark-coloured, heavy woods ; whilst other 

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

 duramen. When, however, we compare heartvvoods microscopi- 

 cally they do as a rule resemble one another in allied species. 



In many cases 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 

 Laivs&nidjia from Oregon, C. Thydides from the Eastern States, 

 Thuya gigdntea, the Canoe Cedar or Red Cedar of the West, and 

 T. occidentdlis, the Arbor-vitse of the North-east, all 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 



