6 The Forests of Canada. 



is found at Cedar Lake near the north-western part of Lake 

 Winnii)eg. Colonies or outlying patches of other trees have 

 l»een noted in ditteront localities, such as of the hasswood 

 and sugar-maple at Lake St, John, north of (Quebec, of the 

 gi-ey elm <m Missinaibi River, near James Bay, and of the 

 hemlock spruce at Thompson, near the west end of Lake 

 Superior. 



JUvers and lakes, by supplying heat and moisture and 

 warding ott' summer frosts, often promote the growth 

 of trees on their immediate banks which are not found 

 elsewhere in the surrounding country. Instances of this 

 may be seen along the North Saskatchewan, where the 

 negundo, green ash, grey elm, white birch, alder, etc., thrive 

 only on the river banks. Tn the cold regions, the white 

 spruce grows to a much larger size on the shores and islands 

 of rivers flowing north than elsewhere. It has been found 

 that exotic fruit trees and other intj-oduced plants can be 

 successfully cultivated around the shores of the larger lakes, 

 especially on their southern sides, which will not grow at a 

 short distance inland. On the other hand, the immediate 

 [)roximity of the sea, with a lower summer temperature 

 than the land, is unfavourable to the growth of timber in 

 the north. The habits of some trees are much modified in 

 different latitudes. Species which grow in warm dry soil 

 in the north may be found in cold, heavy, or wet land in 

 the south. The larch, balsam, white cedar, white pine, 

 white birch, etc., are examples of this tendency. Some 

 species extend far to the south of their general home along 

 mountain ridges, while others seem to refuse to follow such 

 lines. The existence of extensive swamps, the shelter of 

 hills, or the elevations which they afford, are therefore to 

 be regarded as among the minor conditions governing the 

 distribution of trees. 



The peculiarities in the outline of the northward limit of 

 the white cedar and other species of troes, may throw some 

 light on questions as to the direction from which they have 

 migrated or been dispersed. In some cases which the author 

 has studied, the trees appear to have reached the most north- 

 ern limit possible. For example, in its most northern range, 



