226 ANATOMY OF THE GYMNOSPERMS 



A light, soft wood remarkable for its durability in the soil. The tree is the 

 largest produced by American forests, attaining a height of 79-119 m. 

 and a diameter of 6-1 1 m. 



Relative specific gravity 0.2882 



Approximate relative fuel value 28.67 



Coefficient of elasticity in kilograms on millimeters . . 451. 



Ultimate transverse strength in kilograms 196. 



Ultimate resistance to longitudinal crushing in kilograms 6210. 



Resistance to indentation to 1.27 mm. in kilograms . . 1091. 

 (Sargent) 



Western slopes of the Sierra Nevada Mountains, California, from Placer 

 County south to Deer Creek on the southern borders of Tulare County 

 (Sargent). 



3. * * S. Langsdorfii (Brongn), Heer. 



Transverse. Growth rings medium, strongly defined. Tracheids of the 

 spring wood squarish, large, 52 x 52 p., the walls 14 p. thick. Summer 

 wood of 3-6 tracheids in thickness, the transition from the spring 

 wood rather abrupt. Resin cells rather numerous throughout the 

 growth ring and scattering. Resin passages usually absent, but occa- 

 sionally appearing in a rudimentary form on the outer face of the 

 summer wood. 



Radial. Medullary rays devoid of tracheids ; the parenchyma cells equal 

 to about 4 tracheids, somewhat constricted at the ends ; the upper and 

 lower walls thin and entire ; the terminal walls not pitted, straight or 

 curved ; the lateral walls with no recognizable structural details. 



Tangential. Medullary rays i -seriate or rarely 2-seriate in part, the oval 

 or round cells about 31.5 p. broad. 



This very widely distributed and well-known Cretaceous and Tertiary plant, 

 which is chiefly represented by foliage and fruit, is apparently repre- 

 sented also by the woody stem in the Lignite Tertiary of the Porcupine 

 Creek and Great Valley groups in Saskatchewan. Reference of the 

 wood to this species is, however, made provisionally, as the evidence is 

 not such as to warrant an absolute decision. The occurrence of the 

 genus in this locality, however, indicates that it at one time occupied 

 the present prairie region in preglacial times, and that its recession to its 

 present narrow limits probably occurred as the result of glacial action. 



4. * * S. Burgessii, Penh. 



Transverse. Growth rings chiefly narrow but variable, the rather narrow 

 but variable summer wood dense, the transition from the spring wood 

 abrupt. Tracheids of the spring wood large, squarish, and thin-walled. 

 Resin canals wholly wanting. Resin cells numerous throughout the 

 growth ring, but especially on the outer face of the summer wood : 

 with dark, massive resin. Medullary rays chiefly i cell wide, occa- 

 sionally broader and bearing a resin canal with large thyloses. 



