ECONOMIC WOODS OP THE UNITED STATES 75 



a 4 Color varying from light straw or creamy-white 

 to reddish-brown, more pronounced in summer 

 wood and deepening upon exposure to sunlight. 

 Texture comparatively fine. Lustre silky. 

 Wood readily cleavable into long thin strips. 

 Resin ducts fairly conspicuous, especially in 

 second-growth, appearing on longitudinal sur- 

 face as straw-colored or light-brown lines. No 

 sugary exudations. Sp. gr. .35-43. (Eastern) 

 White Pine, Northern Pine, Pinus strobus L. 

 (N) 3 ; Western or Idaho White Pine, P. monti- 

 cola Dougl. (P). 



b 4 Color yellowish-white to very light brown, never 

 deeply reddish; brown stain common. Texture 

 coarse. Lustre dull. Wood not readily 

 cleavable into long thin strips. Resin ducts con- 

 spicuous and usually dark-colored. Sugary 

 exudations and sugar pockets common on fresh 

 lumber. Sp. gr. .32-40. Sugar Pine, P- lam- 

 bertiana Dougl. (P). 4 



b 3 Wood rather hard, cross-grained, fine-textured. 

 Color yellowish, uneven, not very distinct from 

 sapwood. Odor often like beeswax. Sp. gr. .45- 

 .67. Ray parenchyma cells with 3-6 small piciform * pits 

 in each cross-field. (Fig. 5, p. 26.) 



Foxtail and Nut Pine Group. 

 Pifion pine, P. edulis Eng. (R) .f 5 



b 2 Decided contrast in density and usually in color be- 

 tween seasonal growths; transition between the two 

 portions of a growth ring usually abrupt; texture 

 variable, often very uneven. Woods varying from 

 very hard to soft; moderately to highly resinous. 

 Color variable, but mostly darker than in soft pines. 

 Ray tracheids, which often predominate in ray, with upper and 



* Pit with lenticular opening and small circular border as in rays of Picea. 



t Microscopic structures for this group apply also to P. quadrifolia Pari. 

 (P), P. cembroides Zucc. (R), P. monophylla T. & F. (R), P. balfouriana Murr. 

 (P), P. aristata Eng. (P). These woods are not of commercial importance. 



