THE DOUGLAS FIR 101 
and light in weight, or it may be red, coarse-grained, 
and heavier. The wood is close, straight and regular 
in grain, firm, tough, and elastic, not in the least liable 
to warp, and very durable. In appearance it more 
nearly resembles the wood of the Canadian Red Pine 
(Pinus resino’sa Sol.) than any other species; but, 
under the microscope, a longitudinal section shows 
a structure that distinguishes it from all allied woods. 
Its “tracheids,” or elongated vessel-like elements, 
have spiral lines of thickening, especially in the 
spring-wood of each annual ring. Such spiral thick- 
ening occurs throughout the somewhat similiar 
wood of the Yew; but the Yew is non-resinous, while 
the Douglas Fir produces an abundance of resin. 
The transverse section shows the sap-wood and heart- 
wood, resembling those of the Larch, but that the 
latter is of a more rosy red. The annual rings are 
sharply defined by the broad and darker band of 
autumn-wood. This character places the wood of the 
Douglas Fir commercially with the “ Hard Pines.” 
The bark, thin, smooth, and greyish on young shoots 
and warty with resinous pustules a little later, 
becomes from three to five inches thick on old trees, 
splitting into broad, rounded ridges and breaking up 
at its surface into reddish-brown scales. Through 
its longitudinal fissures it discloses a redder inner 
bark. 
In the leaves, and to a less extent in the cones, we 
have those resemblances and differences which justify 
us in making separate genera for the Hemlock Spruces 
and the Douglas Spruce, and at the same time excuse 
the use of the word Spruce in their popular names. 
