TORREYA 
September, 1912 
Vol. 12 Моо. 
THE DETERMINATION OF WOODS * 
By CHESTER ARTHUR DARLING 
As an introduction to this key to the commercial timbers it 
seems desirable to give a few directions and to define a few terms. 
The wood of a tree, like the leaves, is often variable; this variation 
is seen in the width of the growth rings, in the texture, and in 
the color of the wood which may be due to its being either sap or 
heart wood or to the length of time that it has been exposed after 
being cut. 
For determination of any wood, a sample at least an inch 
square in cross section and three inches in longitudinal section 
should be used; a larger piece often shows the characters better 
than a small one. In using the key a hand lens which magnifies 
at least four times and a sharp knife which will make a clean cut 
surface in cross section of the wood without tearing the tissue 
are necessary. Unless otherwise indicated the section cut cross- 
wise of the grain is the one to be examined. When color is to be 
determined the longitudinal section which has been freshly cut 
and not the cross section should be used; it is always best to test 
for color by placing the wood against a white surface. 
Growth rings are indicated by parallel markings more or less 
curved which are seen on the cross section of the wood, usually 
varying in width from gj in. to 1 in.; in the cross section of 
the tree they appear as concentric rings. Where there are 
parallel markings of two distinct types alternating, one of harder 
or more compact wood than the other, the two taken together 
[No. 8, Vol. 12, of TORREYA, comprising pp. 175-200 was issued 9 Aug 1912.] 
be ан accepted; specimens of wood may be obtained upon request; additi 
copies of the key may be secured for 10 cents by addressing the author at Columbia 
University, New York City. 
201 
