FOREST TREES OF THE PACIFIC SLOPE. 



245 



Nebraska, northern Montana, Idaho, and Oregon. West of Hudson Bay. abundant on 

 all Great Plains rivers of Canada, extending northward in Mackenzie River valley to 

 (above lat. 68°) within 40 miles of Arctic Ocean, and westward in Alaska to Bering Sea. 

 Less abundant southward in its western range. 



Fid 106. — PoftuUta balsamifera. 



Alaska. — Yukon River valleys and main tributaries; probably remaining north of 

 Pacific coast ranges, except at Chilkoot Pass (bead of Lynn Canal), where it may 

 descend to south side for a short distance, and at Cook Inlet, where, from Bering 

 Sea forest, it crosses low base of Alaska Peninsula and meets Pacific coast forest. 



