206 



TREES OF NORTH AMERICA 



Distribution. Coast of Alaska from Cook Inlet southward to the head of the 

 Lyun Canal. 



9. Betula Alaskana, Sarg. White Birch. 



Leaves rhomboidal to deltoid-ovate, long-pointed, truncate, rounded or broadly 

 cuueate, or on leading shoots occasionally cordate at the entire base, coarsely and 

 often doubly glandular-serrate above, when they unfold yellow-green and covered 

 with resinous glands, lustrous and villous above and slightly puberulous below, at 



maturity thin, dark green above, pale and yellow-green below, l^'-3' long, !'-!' 

 wide, with slender midribs and primary veins pubescent or ultimately glabrous be- 

 low ; their petioles often bright red, somewhat hairy at first, finally glabrous, about 

 1' long; stipules oblong, gradually narrowed and rounded at the apex, villous partic- 

 ularly toward the margins. Flowers : staminate aments clustered, sessile, 1' long, 

 y thick, with ovate acuminate scales puberulous on the outer surface, bright red, with 

 yellow margins; pistillate aments slender, cylindrical, glandular, 1' long, ' thick, 

 on stout peduncles nearly ^' long. Fruit : strobiles glabrous, pendulous or spread- 

 ing, I'-l^' long, J'-^' thick, their scales ciliate on the margins; nut oval, narrower 

 than its broad wing. 



A tree, usually 30-40, occasionally 80, high, with a trunk 6'-12' in diameter, 

 slender erect and spreading or pendulous branches, and glabrous bright red-brown 

 branchlets more or less thickly covered during their first year with resinous glands 

 sometimes persistent until the second or third season. Winter-buds ovate, obtuse 

 at the gradually narrowed apex, about \' long, with light red-brown shining outer 

 scales sometimes ciliate on the margins, and oblong rounded scarious inner scales 

 hardly more than ' long when fully grown. Bark thin, marked by numerous elon- 

 gated dark slightly raised lenticels, dull reddish brown or sometimes nearly white 

 on the outer surface, light red on the inner surface, close and firm, finally separable 

 into thin plate-like scales. 



Distribution. Valley of the Saskatchewan northwestward to the valley of the 

 Yukon, growing sparingly near the banks of streams in forests of coniferous trees 

 and in large numbers on sunny slopes and hillsides; the common Birch-tree of the 

 Yukon basin. 



