THE WOOD. By 
pines which show a more abrupt transition from early to late wood. 
The width of the annual rings and the proportion of early wood 
to late wood in them are characters which determine the quality 
of western yellow pine wood as recognized by lumbermen. Where 
the growing season is short, and other conditions are unfavorable 
to rapid growth, the greater part of the annual ring consists of early 
wood, and very little contrast 1s seen between the rings, because of 
the small amount of late wood produced. A small proportion of this 
wood means a lack of the more stable wood elements, and hence a 
deficiency in strength. Lumber characterized by layers of growth of 
this type is comparatively brittle, and may be rather easy to work, 
features which permit narrow-ringed grades of western yellow pine 

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c. Tangential 


Fic. 7.—a, transverse, b, radial, and c, tangential sections of western yellow pine, magni- 
fied 20 diameters; a. 7., annual (layer) ring; e. w., early wood; l. w., late wood; 
p. r., pith rays; r.-d., resin ducts; t., tracheids; f. t., flattened tracheid. 
to be substituted for white pine. Where, however, the growing sea- 
son is longer and conditions are favorable to rapid growth the ring 
produced each season is much wider, and shows a strong contrast be- 
tween its early and late wood, the latter being particularly abundant. 
The cell elements in the late wood of trees grown under these con- 
ditions are stronger, more durable, and as a result of the large pro- 
portion of late wood the lumber of fully matured trees is of the 
best quality. Resin ducts, which are conspicuous in this wood and 
easily observed in a smooth transverse section (fig. 6 a, 7. d.), are 
confined, in annual rings of average width, to the transitional part 
of the ring between the early and late wood, but in very narrow rings 
resin ducts are usually present only in the late wood. These charac- 
teristics are, to some extent, helpful in distinguishing western yellow 

