290 ANATOMY OF THE GYMNOSPERMS 



tracheids with thyloses ; the epithelium cells very much flattened, 

 rather thin-walled. Medullary rays rather prominent, i cell wide, 

 rather numerous, distant 2-8 rows of tracheids. 



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

 ginal, sometimes interspersed. Parenchyma cells straight or rarely 

 narrower at the ends, long ; the terminal walls coarsely pitted ; the 

 upper and lower walls medium, sinuately unequal, distantly and often 

 obscurely pitted except in the summer wood ; the lateral walls with 

 small, oval, bordered pits with a lenticular orifice, 2-6 per tracheid, 

 more rarely 2 throughout, in the summer wood reduced to 2, and 

 finally to i. Bordered pits numerous, crowded, round, or elliptical, the 

 orifice large, round, becoming narrow in the summer wood and par- 

 allel with the tracheid axis. Pits on the tangential walls of the sum- 

 mer wood very narrow and small, but generally numerous. 



Tangential. Fusiform rays very narrow and high ; the cells small and thick- 

 walled ; the terminals very long and linear, often unequal ; the resin 

 canal rather small and narrow, oblong. Ordinary rays very narrow, 

 the cells very equal and uniform, oblong and narrow at least in the 

 higher rays, more rarely rather broad and oval. 



A tree 15-21 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 0.4594 



Percentage of ash residue 0.27 



Approximate relative fuel value 45-71 



Coefficient of elasticity in kilograms on millimeters . . iioo. 



Ultimate transverse strength in kilograms 318. 



Ultimate resistance to longitudinal crushing in kilograms 6520. 



Resistance to indentation to 1.27 mm. in kilograms . . 1240. 

 (Sargent) 



Abundant in Newfoundland and in every part of Canada except southern 

 Ontario and the prairie region, ranging northward to latitude 65, where 

 it terminates in association with Betula papyrifera (Macoun). Through 

 the northern United States to Pennsylvania, central Michigan, Wiscon- 

 sin, and Minnesota, and along the Allegheny Mountains to the high 

 peaks of North Carolina (Sargent). 



Pleistocene deposits at Hamilton (Erie clays), Ontario ; the Moose River, 

 Ontario ; Don Valley and the Leda Clays, Montreal. This plant occurs 

 in considerable abundance and is essentially typical of the Don period, 

 where it is associated with another undescribed species, possibly the same. 



Material preserved in a natural state, though usually much altered by 

 decay. 



10. P. sitchensis, Can-. 

 Tideland Spruce. Sitka Spruce 



Transverse. Growth rings thickish. Summer wood very prominent, equal to 

 or exceeding the spring wood from which the transition is gradual, not 

 very dense. Spring tracheids commonly strongly rounded-hexagonal, 



