518 NORTH AMERICAN FAUNA. [no. 27. 



the bulk of the forest. In exposed situations near Leith Point it is 

 somewhat dwarfed, seldom exceeding a diameter of 1 foot and a 

 maximum height of 40 feet. A few miles back from the shore, in 

 slightly more favorable locations, trees 2 feet in diameter at the 

 base were seen, but none of these exceeded 50 feet in height. A tree 

 12 inches in diameter, growing in an exposed situation near the 

 shore, had 257 annual rings. In this specimen the outer layers were 

 exceedingly thin and could be counted only by the aid of a fine- 

 pointed needle. At this rate, the age of a tree of twice this diameter 

 can scarcely be estimated at less than 1,000 years. (PI. XXIV, fig. 

 1.) Farther west along the shore the species attains greater perfec- 

 tion of habit, especially in some of the sheltered bays. At Fort 

 Franklin it is the commonest tree, but at present is represented by 

 scarcely any individuals of the original forest, which has been re- 

 moved for building purposes. Trees over 8 or 9 inches in diameter 

 are rare. A sapling 4 feet in height and 1 inch in diameter, on the 

 site of Fort Franklin, had been growing for thirteen years. 



On the Mackenzie it does not attain the size reached farther south, 

 but is still a stately tree. One measured lyy Richardson on the Mac- 

 kenzie above Fort Norman was 122 feet in height. On the alluvial 

 banks and islands of the lower Mackenzie and Peel rivers it attains 

 a diameter of 18 inches. 



On the northern slopes of the mountains near the mouth of the 

 Nahanni this tree ascends to timberline, but above an altitude of 500 

 feet seldom exceeds a height of 25 feet (PL XXIV, fig. 2). 



In the region to the eastward of Great Slave Lake it reaches its 

 northern limit on Artillery Lake and on Thelon River, where isolated 

 groves extend to latitude 62° 22', well within the general confines of 

 the Barren Grounds. 



Picea mariana (Mill.) B. S. P. Black Spruce. 



The black spruce extends northward nearly to the limit of the for- 

 est, but is confined mainly to the muskegs, seldom growing on the 

 alluvial bottom lands, where the white spruce attains its perfection. 

 It furnishes a poorer quality of lumber than the white spruce, and is 

 put to fewer uses. I noted it in places all along the main route to the 

 mouth of the Mackenzie and on my canoe route to the eastward nearly 

 to Great Bear Lake. A tree 4 inches in diameter, growing in a shel- 

 tered situation on Lake Hardisty, had 78 annual rings, and a sapling 

 1 inch thick at the base, near the same locality, had been growing 

 fifteen years. This species ascends the northern slopes of the moun- 

 tains at the mouth of Nahanni River to timberline at about 2,000 feet. 



Abies balsamea (Linn.) Mill. Balsam Fir. 



The balsam fir occurs rather commonly along the Athabaska from 

 Athabaska Landing to the delta. On the lower part of the river it 



