1903-4. | How Pvanr LiFe Is DISTRIBUTED IN CANADA AND WHY. 33 
It is a remarkable fact, that a considerable number of forest trees of 
Ontario in their range westward, come to an abrupt termination in Can- 
ada in the district lying between Lake Superior and the Lake-of-the- 
Woods, whilst others are hardly seen west of Sault Ste. Marie. in On- 
tario there are seventy-six species of forest trees, of which thirty-six 
are known either on the north or the south shores of Lake Superior. Of 
these thirty-six, only thirteen cross into the prairie region in central and 
southern Manitoba. Similar circumstances are apparent in an even 
greater degree among the shrubs and herbaceous plants. In Canada, 
many of these seem to be limited in their western course by the outlet 
of Lake Superior, though in the United States they may be found to the 
southward of this lake. Lake Superior is a large body of cold water 
whose surface at fifty miles from land, has been found even in July, to 
have a temperature as low as 3914° Fahrenheit. In this respect it is 
quite different from the other lakes. The effect of this low temperature on 
the vegetation of the immediately surrounding land is very marked, 
making it a suitable home for some semi-Arctic plants. Further reasons 
for this limit in westerly range are readily understood when the rocky, 
hilly nature of the country around the northern coasts of this lake and 
the more boreal character of the climate generally there, are considered. 
The rough nature of the country immediately to the westward of 
Lake Superior—being successions for over 300 miles of rocky hills, swamps, 
and large and small lakes with their connecting rivers—has had, no doubt, 
its influence in limiting the distribution of many species there. It, 
however, appears also suggestive that the gradual widening in the past by 
forest and prairie fires, of the prairie area in a direction easterly from 
the Red River, has been a leading cause in checking the farther west- 
ward extension of so very many of the eastern trees, shrubs and herba- 
ceous plants presently found in the country to the east of the Lake-of- 
the-Woods. 
The interesting points in the Boreal Group are the occurrence of some 
of the species on the Lower St. Lawrence coasts and, again, around 
Lake Superior. In both cases these semi-Arctic or high northern plants 
are found, not on Alpine summits, but at or near the water level. Refer- 
ence has already been made to the influence on plant life, especially on 
the northern shores, of the cold deep waters of Lake Superior, an in- 
fluence that does not extend very far inland and suggests whether the 
semi-Arctic plants found on the immediate coast may not be the relics 
of the Arctic plant life which in Pleistocene times or previously, no doubt, 
occupied this region. On the Lower St. Lawrence we find a similar 
representation of high northern plants. The cold and broad Boreal 
current which skirts the Labrador coasts sends a branch through the 
