GEOGRAPHICAL DISTRIBUTION OF FOREST TREES IN CANADA. 293 



TREE-LINES IN MINNESOTA. 



The State of Minnesota is situated in a very interesting region in regard 

 to forest distribution. Here we find the northern limit of the group of 

 trees to which the most southern species of Ontario belong, such as the 

 black walnut, buttonwood, shell-bark hickory, hackberry, and Kentucky 

 coffee-tree ; the north-western limit of the commoner trees of the northern 

 States and of Quebec and Ontario, such as the white oak, red cedar, iron- 

 wood, white ash, rock elm, red oak, yellow birch, sugar maple, red maple, 

 etc. ; the western boundaries of some of the trees whose northern limits 

 pass through northern' Ontario, such as the white cedar, black ash, white 

 pine, and red pine ; the southern limits of the most northern group, in- 

 cluding the white and black spruce, the larch, Banksian pine, balsam fir, 

 balsam poplar, and canoe birch ; and the general eastern limits of some 

 of the western species, such as the negundo or Manitoba maple, the 

 green ash, and the cottonwood. The boundaries of the trees of Minnesota 

 have been mapped out by Professor N. H. Winchell, State geologist. 



THE GREAT NORTHERN FOREST. 



Reference has already been made to the great northern forest of Canada, 

 which stretches from the Strait of Belle Isle round by the southern end 

 of James Bay to Alaska, a distance of about 4000 miles, with a breadth 

 of some 700 miles. This vast forest has everywhere the same character- 

 istic features. The trees, as a rule, are not large, and they consist 

 essentially of the following nine species : black spruce, white spruce, 

 Banksian pine, larch, balsam fir, aspen, balsam poplar, canoe birch, and 

 bird cherry, with several kinds of small willows, which, however, seldom 

 attain the size of trees. White cedar, white and red pine, black ash, and 

 rowan occur sparingly in the southern part of this belt. 



FIRES AND SECOND GROWTH. 



As a rule, any extensive view over this vast region presents a " patchy " 

 appearance, owing to the different shades of green covering larger or 

 smaller areas. These various shades indicate growths of different ages, 

 which commenced after forest fires at different periods ; but ultimately 

 the trees all go through the same stages, and arrive at maturity in the same 

 number of years. These patches may be of limited extent, or they may 

 embrace many thousands of square miles, but a uniform process is going 

 on in each of them. It begins with the complete destruction by fire of 

 the preexisting growth of trees, and ends with a burning of the newly 

 matured forest similar to that which preceded it. 



FOREST FIRES ARE NATURAL PHENOMENA. 



These fires are natural phenomena, being mostly due to lightning in the 

 summer-time, and they have no doubt been going on from time im- 

 memorial. Lightning is of frequent occurrence during the hot, dry season 



