438 



Butler : The western American birches 



This birch is distinguished by its thin bright green doubly 

 serrate leaves with fine very slender lanceolate-attenuate teeth, 

 curved toward the apex, by the slender, very resinous branchlets, 

 and by the orange or bronze bark with its curling, shreddy, outer 



Wash 



Figure i6. Betula occidentalis Hook. From B. T. Butler jjg. Yellow Bay, 

 Flathead Lake, Montana. 



layer. It is common along the Pacific Coast region of 

 and British Columbia, reaching eastward to western Montana, 

 where it is found along the Kootenai River and about the shores 

 of Flathead Lake. It is locally known as yellow birch, black 

 birch, and western birch. 



i 



17. Betula montanensis sp. nov. 



A large tree with dark gray or brown bark often mottled with 

 orange or bronze, somewhat roughened but not peeling into shreds 

 or separating into layers, lenticels 2-4 cm. long, inner bark reddish 

 brown, very dark ; branchlets red-brown, more or less resinous, 

 becoming ashy gray and much roughed by leaf-scars ; leaf-blades 

 4-6.5 cm. long, 3-5.5 cm. wide, thick and firm, dull bronze-green, 

 glabrous, slightly lobed, ovate, apex acute, base truncate, often 

 subcuneate on young leaves, margins finely serrate with abruptly 



