PINUS 321 



17. P. Banksiana, Lamb. 



Scrub Pine. Gray Pine. Jack Pine 



Transverse. Growth rings narrow, uniform. Summer wood dense, about 

 one half the spring wood, from which the transition is generally abrupt; 

 the tracheids in regular rows, rather uniform. Spring tracheids con- 

 spicuously squarish, uniform in regular rows, the walls thin. Resin 

 passages rather small, rather numerous, widely scattering ; the epithe- 

 lium in 1-2 rows of thin-walled cells, those of the first row much 

 flattened, those of the second row large, irregularly rounded and resin- 

 ous, with an occasional thick-walled cell, the whole forming an eccentric 

 tract. Medullary rays not very broad, somewhat prominent, distant 

 2-10 rows of tracheids. 



Radial. Rays sparingly resinous ; the ray tracheids strongly predominant 

 and for the most part strongly reticulated throughout, interspersed. 

 Ray cells of I kind only, short fusiform and equal to about 4 spring 

 tracheids ; the terminal walls thin and not pitted ; the upper and lower 

 walls variable, sometimes very thin and entire, or again thicker and 

 unequal ; the lateral walls with very irregularly oval or lenticular and 

 unequal pits, 1-6 per tracheid, in the summer wood becoming i. 

 Bordered pits in i row, sometimes in pairs or again distinctly 2-rowed, 

 elliptical, becoming smaller and more distant toward the summer wood, 

 where they are quickly reduced and are finally obscure or wanting. Pits 

 on the tangential walls of the summer wood wholly wanting. 



Tangential. Fusiform rays rather low and narrow, rather few ; the terminals 

 acute or somewhat prolonged and chiefly composed of tracheids ; the 

 cells of the inflated portion large and rather thin-walled, generally all 

 present. Ordinary rays low and chiefly narrow, presenting three prin- 

 cipal aspects: (i) low rays composed of oblong or narrowly oval, 

 thin-walled parenchyma cells with narrowly oblong, terminal tra- 

 cheids ; (2) low rays of similar composition, but the parenchyma cells 

 much thinner-walled ; and (3) the highest rays composed chiefly of 

 narrow tracheids with a few broader, oblong parenchyma cells inter- 

 spersed. 



A small tree 9-22 m. high, with a trunk rarely exceeding .75 m. in diameter. 

 Wood light, soft, not strong, rather close grained, and compact. 



Specific gravity 0.4761 



Percentage of ash residue 0.23 



Approximate relative fuel value 47-5 



Coefficient of elasticity in kilograms on millimeters . . 942. 



Ultimate transverse strength in kilograms 278. 



Ultimate resistance to longitudinal crushing in kilograms 6329. 



Resistance to indentation to 1.27 mm. in kilograms . . 1609. 

 (Sargent) 



Halifax, Nova Scotia, northwesterly to the Athabasca River and down the 

 Mackenzie River to the Arctic Circle ; eastward it hardly becomes a tree, 

 but westward it increases in size, and westward of Lake Winnipeg it 



