520 NORTH AMERICAN FAUNA. [no. 27. 



zie at Fort Simpson it is a stately tree, but below that point it rap- 

 idly decreases in size, and on the lower Mackenzie and Peel rivers 

 occurs only as a small tree. Its wood is put to very little use except 

 for fuel, and even for this purpose it is not well adapted. 



In 1903, at Brule Rapid, Athabaska River, its catkins opened on 

 May 2G. On May 30, on the lower Athabaska, its leaves had expanded 

 sufficiently to be conspicuous, and they were nearly full grown on 

 Rocher River on June 6. 



At Fort Simpson, on May 18, 1904, the leaves on the balsam pop- 

 lars were just starting, but on account of a cold rainy period follow- 

 ing they were only half grown on June 2, and were in about the same 

 stage at Fort Norman on June 11. 



On the canoe route north of Great Slave Lake I last noted it near 

 the northern end of Lake Hardisty, and I next saw it on the upper 

 part of Bear River, while descending that stream to the Mackenzie. 



J. W. Tyrrell states that a few trees, the last outliers of the species 

 in that direction, were seen on Fairehild Point at the eastern ex- 

 tremity of Great Slave Lake.' 1 



Popuhis tremuloides Michx. Aspen Poplar. 



The aspen poplar occurs nearly throughout the wooded region. 

 In favorable places along the Athabaska and Slave (see PI. VI, 

 fig. 2), it attains a large size, and this is the case also about Fort 

 Simpson. Northward and eastward of these valleys it reaches 

 only a moderate size. On the most exposed parts of the southern 

 shore of Great Bear Lake it occurs only as a dwarfed tree, but west 

 of Mc Vicar Bay it reaches a fair size. On the lower Mackenzie and 

 Peel rivers it seldom attains a diameter of more than 6 inches. East 

 of the Great Slave Lake region it was found by the Tyrrell brothers 

 to extend north to Daly Lake on Telzoa River. 



In 1903 the leaves of the aspens were first seen, near Little Buffalo 

 River, on the morning of May 26, and made much progress during 

 that day. During that autumn, on the southern shore of Great Bear 

 Lake, the leaves had turned yellow on September 14. 



In 1904, at Fort Simpson, the aspen leaves first showed on May 13, 

 and on the following day were half an inch in length. A cold spell 

 which followed retarded their growth, and they were only half grown 

 by June 2, and were at the same stage at Fort Norman on June 11. 



The species is of little economic importance in the north, being 

 used only for firewood. 



Salix padophylla Rydberg. 



Specimens collected on the slopes of the Nahanni Mountains on 

 June 6, 1904, are referred to this species by P. A. Rydberg. The 



"Ann. Kept. Dept. Interior (Canada), 1900-1901, p. 110 (p. 15 of separate), 

 1902. 



