222 ANATOMY OF THE GYMNOSPERMS 



the upper and lower walls medium, with conspicuous, though often 

 distant, simple pits ; the lateral walls with small, oval pits with an 

 oval or lenticular, rather large, orifice, 1-4, or in the marginal cells 

 and low rays 7 per tracheid. Bordered pits elliptical in one row, some- 

 times in pairs, those of the summer wood finally obscure and wanting. 

 Pits on the tangential walls of the summer wood small, often obscure, 

 frequently very distant and confined to the outermost tracheid wall. 

 Resin cells 15-40 p. wide. 

 Tangential. Rays low and narrow, the cells uniformly narrow, oblong. 



A tree 12-18 m. in height and 1.20-1.50 m. in diameter, producing a light, 

 soft, and very durable wood. 



Relative specific gravity 0.3164 



Approximate relative fuel value 3 r -53 



Coefficient of elasticity in kilograms on millimeters . . 533. 



Ultimate transverse strength in kilograms 219. 



Ultimate resistance to longitudinal crushing in kilograms 4903. 



Resistance to indentation to 1.27 mm. in kilograms . . 957. 

 (Sargent) 



Rare in Nova Scotia; abundant in New Brunswick, Quebec, and Ontario, 

 and northward to Hudson's Bay ; westward to Lake Winnipeg and the 

 mouth of the Saskatchewan in latitude 53 30' N. (Macoun); southward 

 to New Jersey and through the Alleghenies to North Carolina (Britton) ; 

 thence westward through New York and Pennsylvania to central Michi- 

 gan, northern Illinois, and central Minnesota (Sargent). 



This species is a well-defined and somewhat abundant constituent of the 

 Pleistocene flora in the Don Valley at Toronto, and the Leda clays of 

 Montreal ; Leda River, Manitoba, and Marietta, Ohio. An undescribed 

 species of Thuya also occurs in the Lignite Tertiary, Saskatchewan, 

 probably of the Porcupine Creek and Great Valley groups. 



3. T. japonica, Max. 



Jap. = Xedziiko 



Transverse. Growth rings rather narrow, variable ; the prominent summer 

 wood very narrow, of about 6 tracheids, or again upwards of 16 tra- 

 cheids, rather dense, the transition to the spring wood gradual. The 

 broad spring wood open ; the tracheids rather large, conspicuously 

 hexagonal, very thin-walled, in regular rows, uniform. Resin cells 

 prominent and dark, few and widely scattering, chiefly in the summer 

 wood. Medullary rays not prominent, sparingly resinous, i cell wide, 

 narrow, distant 2-18 tracheids. 



Radial. Rays very sparingly resinous, rarely with tracheids. Cells chiefly 

 straight, the upper and lower walls rather thin, uniform, and fre- 

 quently pitted ; the terminal walls thin, very commonly curved, not 



