PICEA 285 



3. * P. alba, Ait. 



White Spruce 



Transverse. Growth rings thick. Summer wood thin, rather prominent, 

 upwards of one fourth the spring wood from which the transiton 

 is gradual, rarely abrupt ; the structure rather dense ; the tracheids 

 conspicuously squarish. Spring wood open, the tracheids squarish- 

 hexagonal, uniform in very regular rows, the walls thin. Resin pas- 

 sages scattering, rather large, round, commonly without thyloses, 

 equal to 2-3 tracheids ; the epithelium of very unequal, chiefly narrow, 

 and rather thin-walled cells. Medullary rays not very numerous, 

 rather prominent, narrow, i cell wide, distant 2-14 rows of tracheids. 



Radial. Rays very sparingly resinous; the ray tracheids prominent, mar- 

 ginal, sometimes interspersed in the higher rays. Ray cells straight 

 throughout, equal to 5-13 spring tracheids ; the terminal walls coarsely 

 pitted ; the upper and lower walls rather thin, unequal, sparingly pitted 

 in the spring wood, strongly pitted in the summer wood; the lateral 

 walls with numerous small, oval pits with a lenticular orifice, 2-6 per 

 tracheid, in the summer wood abruptly reduced to 2, and finally to i. 

 Borderedpitsin i row, numerous, round, or elliptical, the orifice large; in 

 the summer wood becoming remote and finally obscure, the orifice usu- 

 ally a prolonged slit. Pits on the tangential walls of the summer wood 

 very flat and obscure, chiefly confined to the outermost tracheid wall. 



Tangential. Rays rather numerous, nonresinous, low to high. Fusiform 

 rays narrow, the cells thin-walled, the resin canal small, the epithelium 

 composed of thick-walled cells. Ordinary rays narrow, not conspic- 

 uously contracted by the occasionally interspersed tracheids ; the cells 

 very equal and uniform, oblong, narrow. 



A tree 15-50 m. high, with a trunk upwards of .90 m. in diameter. 

 Wood light, soft, not strong, close and straight grained, compact, satiny. 



Relative specific gravity 0.4051 



Percentage of ash residue 0.32 



Approximate relative fuel value 4-38 



Coefficient of elasticity in kilograms on millimeters . . 1023. 



Ultimate transverse strength in kilograms 319. 



Ultimate resistance to longitudinal crushing in kilograms 5489. 



Resistance to indentation to 1.27 mm. in kilograms . . 1117. 

 (Sargent) 



According to Bovey the following data have been obtained : 



Coefficient of strength in pounds for : 



Bending '. 5 



Torsion 9 



Compression 3200 



Shear 360 



Weight of i cubic foot 3 



Newfoundland, Anticosti, Nova Scotia, and New Brunswick, westward 

 through Quebec and Ontario to the forest limit of Manitoba ; in the 



