PSEUDOTSUGA 275 



2. P. macrocarpa, Mayr. 

 Hemlock 



Transverse. Growth rings broad, variable, the dense summer wood com- 

 posed of rather small, rounded tracheids in irregular rows, upwards 

 of one third the spring wood, from which the transition is gradual. 

 Spring tracheids rather large and squarish-hexagonal, the walls 

 medium, rather uniform in regular rows. Medullary rays promi- 

 nent and resinous, numerous and wide, chiefly i cell wide, distant 

 1-6 rows of tracheids. Resin passages numerous but scattering, 

 equal to about 2 tracheids. Resin cells numerous and prominent on 

 the outer face of the summer wood, and at once recognizable by 

 their color, position, and structure. Resinous tracheids sometimes 

 present and forming small groups or radial series in contact with the 

 rays. 



Radial. Rays sparingly resinous throughout, the tracheids narrow, mar- 

 ginal, or sometimes interspersed. Ray cells straight or contracted at 

 the ends, equal to 6-10 spring tracheids; the upper and lower walls 

 medium, sparingly pitted except in the summer wood ; the terminal 

 walls chiefly rather thin and not very strongly pitted ; the lateral 

 walls with prominent and resinous pits conspicuously much larger 

 than in P. Douglasii, the border prominent, the orifice at first len- 

 ticular, at length oblong, at first 3-6 throughout the spring wood, 

 somewhat abruptly reduced to i per tracheid in the summer wood. 

 Bordered pits numerous in i row, strongly elliptical. Pits on the 

 tangential walls of the summer tracheids few, very small and obscure. 

 Resin cells upwards of 50 /u, wide and 135-300 p, long. Spirals more 

 or less obscure, often distant, finally vestigial and in the summer 

 wood wanting, the angle 70. 



Tangential. Fusiform rays lenticular or the terminals unequally linear, 

 narrow, the central tract with i small resin canal. Ordinary rays 

 sometimes 2-seriate in part, resinous, broad, medium to high ; the 

 cells often very unequal, rather uniform, squarish, more rarely oval 

 or round. Rays much more numerous than in P. Douglasii. 



A tree 30-54 m. in height, with a trunk of 1.08 m. in diameter. 



Wood heavy, hard, strong, cross grained, very durable, difficult to work. 



Relative specific gravity 0.4563 



Percentage of ash residue 0.08 



Approximate relative fuel value 45-59 



Coefficient of elasticity in kilograms on millimeters . . 1050. 



Ultimate transverse strength in kilograms 361. 



Ultimate resistance to longitudinal crushing in kilograms 7405. 



Resistance to indentation to 1.27 mm. in kilograms . . 1642. 

 (Sargent) 



Dry ridges and canons between 2500 and 4000 feet elevation ; the coast 

 ranges of California ; San Bernardino Mountains to the Cuyamaca 

 Mountains (Sargent). 



