PICKA 287 



This tree characterizes the interior plateau of British Columbia, with the 

 exception of the dry southern portions, forming dense groves in the 

 mountains. It ranges northward to latitude 54 7' 34" at an altitude of 

 2600 feet (Macoun). Dry gravelly ridges and slopes between 5000 and 

 11,500 feet elevation, constituting the most valuable timber tree of the 

 central Rocky Mountains, where it forms extensive forests, generally 

 above 8500 feet elevation. Rare and of small size in the mountains of 

 Washington, Oregon, and Montana (Sargent). 



5. P. jesoensis, Carr. 



Jap. =. To hi 



Transverse. Growth rings narrow, uniform. The very thin summer wood 

 open and composed of 5-10 tracheids, about one fourth the spring 

 wood, from which the transition is rather gradual. Spring tracheids 

 large, squarish-hexagonal, thin-walled, very unequal but in regular 

 rows. Resin passages not very numerous, chiefly large, with thyloses, 

 the epithelium of very unequal, rather thick-walled cells. Medullary 

 rays not numerous, rather resinous and prominent, i cell wide, dis- 

 tant 2-8 rows of tracheids. 



Radial. Rays sparingly and locally resinous ; the ray tracheids prominent 

 and often interspersed. Ray cells somewhat contracted at the ends, 

 equal to 3-7 spring tracheids ; the terminal walls coarsely pitted ; the 

 upper and lower walls not very thick, conspicuously pitted, especially 

 in the summer wood ; the lateral walls with small, oval, bordered pits 

 with a narrow orifice, 3-5 per tracheid, in the summer wood reduced 

 to 2, and finally to i. Bordered pits large, strongly elliptical, in i row, 

 rather numerous, often in compact rows towards the ends of tracheids. 

 Pits on the tangential walls of the summer wood rather few, small, 

 and inconspicuous. 



Tangential. Rays not very numerous, low to medium, sparingly resinous. 

 Fusiform rays rather broad, the rather large resin canal with thick- 

 walled epithelium, chiefly without thyloses. Ordinary rays not very 

 broad, contracted at the position of the sparingly interspersed tra- 

 cheids ; the cells rather thick-walled, very equal and uniform, narrowly 

 oblong, rarely oval. 



6. P. polita, Carr. 



Jap. = Iramomi 



Transverse. Growth rings thin, very variable. Summer wood prominent, 

 rather dense but variable, from 3 tracheids thick upwards, equal to 

 one half to one third the spring wood from which the transition is 

 rather gradual; the tracheids variable. Spring tracheids rather large 

 and thin-walled, uniform in regular rows. Resin passages rather 

 numerous, large but variable, equal to 1-4 tracheids, with thyloses; 

 the epithelium of very unequal, rather thin-walled cells. Medullary 

 rays rather numerous and broad, i cell wide, resinous, distant 2-8 or 

 lo rows of tracheids. 



