TRANSACTIONS OF SECTION F. 857 



throughout the great distance of 4,000 miles we find the same group of trees. 

 Again in the great triangular area of the North-west, between the United States 

 boundary, the Rocky Mountains, and the Laurentian region, embracing over 600,000 

 square miles, very little difference could be observed in the climate, the soil, or the 

 general level of the country, and hence the same group of trees— only about half a 

 dozen in all — are found throughout this immense tract. In striking contrast with 

 this is the fact that on the same farm lot in the south-western part of the province 

 of Ontario one may often count as many as fifty different trees. The richness in 

 variety of the native trees of Ontario and the adjacent States is owing to the 

 fertile soil and the favourable conditions as to summer temperature, constant mois- 

 ture, and the absence of intense cold in the winter. The writer exhibited a map 

 showing the northern and western limits of the principal forest trees of the Do- 

 minion east of the Rocky Mountains. From this it appears that the range of species 

 is not according to the mean annual temperature or precipitation, but rather to the 

 absence of extremes of heat and cold, and great dryness. For these reasons a 

 number of the trees of the province of Quebec and northern Ontario do not range 

 west into Manitoba, although the annual means of temperature and precipitation 

 are nearly the same in both. This map also shows in a striking manner that the 

 northern limits of our various forest trees are by no means parallel to one another, 

 although locally some groups may be nearly so for a certain distance. Some of 

 them pursue extraordinary or eccentric courses, which are difficult to account for. 

 The most remarkable of these is the white cedar, which hi the central part of its- 

 trend reaches James' Bay, but drops suddenly to the south at the Gulf of St. Law- 

 rence in the east, and on reaching the longitude of the head of Lake Superior in the 

 west. Yet the climate and other conditions appear to be the same for some distance 

 both east and west of these lateral boundaries. An outlying colony of the white 

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

 Colonies or outlying patches of other trees have been noted in different localities, 

 such as of the bass wood and sugar-maple at Lake St. John, north of Quebec, of the 

 grey elm on the Missinaibi River, near James' Bay, and of the hemlock spruce at 

 Thompson, near the west end of Lake Superior. Rivers and lakes, by supplying heat 

 and moisture and warding oft* 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, &c, thrive only on the river banks. In 

 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 introduced 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 proximity 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, 

 &c, 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 among the minor elements govern- 

 ing the distribution of trees. 



The peculiarities in the outline of the northward limit of the white cedar and 

 other species of trees 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 northern limit possible. For 

 example, in its most northern range, the first tender leaves and shoots of the black 

 ash are blighted almost every year by the spring frosts ; the trees are of small size 

 or stunted in height, and only occasionally bear seed. Sir John Richardson 

 mentions that on the barren grounds, outlying patches of dying spruces were some- 

 times met with far out from the verge of the main forest, and that he saw no 

 evidence of young trees springing up beyond the general line of trees ; from which 



