286 ANATOMY OF THE GYMNOSPERMS 



prairie region being found in the sand hills bordering the first prairie 

 steppe. Occasionally in the valley of the Saskatchewan and on the 

 Bow River from Calgary, where it is mixed with P. Engelmanni ; on the 

 Athabasca to latitude 54 7' 34" (Macoun). Coast of Maine through 

 northeastern Vermont and westward through northern Michigan and 

 Minnesota to the Black Hills of Dakota ; along the Rocky Mountains of 

 Montana, where it reaches its greatest development along streams and 

 lakes in the Flathead region, at elevations of 2500-3500 feet (Sargent). 



Pleistocene of the Scarborough period of which it is characteristic, at 

 Scarborough Heights, Ontario. 



Material preserved in the natural state, but showing the effects of exten- 

 sive decay. 



4. P. Engelmanni, Engelm. 



IVhite Spruce. Engelmanri 's Spruce 



Transverse. Growth rings broad. Summer wood very prominent and 

 rather open, about one half to one third the spring wood, from which 

 the transition is gradual ; the tracheids often much compressed radially. 

 Spring tracheids rounded-hexagonal, unequal in regular rows, the 

 walls thin. Resin passages without thyloses, not very numerous ; the 

 epithelium cells very unequal, rather thin-walled. Medullary rays not 

 very prominent, narrow, I cell wide, distant 2-7 rows of tracheids. 



Radial. Rays nonresinous; the ray tracheids prominent, marginal. The 

 ray cells generally straight and equal to 7 spring tracheids ; the ter- 

 minal walls strongly pitted ; the upper and lower walls medium and 

 sparingly pitted, except in the summer wood ; the lateral walls with 

 small, oval, and at first narrowly bordered pits, 2-5 per tracheid, in 

 the summer wood gradually reduced to i. Bordered pits in i row, 

 large, not very numerous, round or elliptical, the orifice finally becom- 

 ing a prolonged slit upwards of 34 p.. Pits on the tangential walls of 

 the summer wood small and not prominent, chiefly confined to the 

 outermost wall. 



Tangential. Rays rather numerous, medium to high, nonresinous. The 

 fusiform rays rather broad, the resin canal large and round, with 

 thick-walled epithelium. The ordinary rays rather narrow, the cells 

 very equal and uniform, narrowly oblong, rarely broader. 



A large tree 24-26 m. high, with a trunk upwards of 1.20 m. in diameter. 

 Wood very light, soft, not strong, very close and straight grained, com- 

 pact, satiny. 



Relative specific gravity 0.3449 



Percentage of ash residue 0.32 



Approximate relative fuel value 33-38 



Coefficient of elasticity in kilograms on millimeters . . 808. 



Ultimate transverse strength in kilograms 245. 



Ultimate resistance to longitudinal crushing in kilograms 4271. 



Resistance to indentation to 1.27 mm, in kilograms . . 1217. 

 (Sargent) 



