524 NORTH AMERICAN FAUNA. [no. 27. 



important species north to the delta. East of the territory covered 

 by our observations Tyrrell observed trees large enough to furnish 

 bark for canoes at the north end of Selwyn Lake; Hanbury noted 

 the species on upper Dease River in 1902. 



This birch opens its leaves about the same time as the aspen poplar. 

 At Fort Simpson, in 1904, the leaves first showed on May 13, and 

 were half an inch long on the following day. They were not fully 

 out, however, until over two weeks later. 



This tree is of great economic importance to the natives of the 

 region. Its wood, though soft when green, is rather hard when sea- 

 soned, and takes a high polish. The frames of snowshoes, the runners 

 of sleds and toboggans, and the handles of axes and other tools are 

 usually made of it. In addition to furnishing the covering for 

 canoes, its bark is used in the construction of baskets and various 

 household utensils, and to some extent for constructing shelters. 



The natives gather the sap in spring and boil it down into sirup. 

 An incision is made with the axe on the side of the tree, and the sap 

 gathers and drops from a projecting point of bark. At Fort Simp- 

 son, in 1904, the sap was running freely from April 20 to May 1. 



Betula alaskana Sarg. Alaskan Birch. 



This species, which seems to be related to B. ocddentalis of Hooker, 

 was collected by Alfred E. Preble and Merritt Cary at Fort McMur- 

 ray. We did not detect it elsewhere. 



Betula glandulosa Michaux. Dwarf Birch. 



Throughout the region now under review northward into the Bar- 

 ren Grounds dwarf birches of one or more species occur. In the 

 Hudsonian zone the larger one, B. glandulosa, which is common in 

 the southern part of the region, is largely replaced by a more dwarfed 

 species, with smaller and more rounded leaves, B. nana of the present 

 report. Both species, however, were found growing side by side at 

 Fort Good Hope and at Fort McPherson. 



Betula nana Linn. Northern Dwarf Birch. 



This species occupies favorable situations — marshes and borders of 

 streams — practically throughout the Hudsonian zone. Dwarf birches 

 believed to belong to this species were collected near Lake St. Croix, 

 at Fort Good Hope, and on the Nahanni Mountains, and the form 

 was common along the shore of Great Bear Lake, and on the Macken- 

 zie from Fort Norman to the delta. - Its seeds furnish a favorite food 

 for the smaller seed-eating birds during the early autumn. 



At Fort Franklin its leaves were falling on September IS, 1903, 

 and in the following spring, on the lower Mackenzie, its foliage 

 opened about the middle of June. 



