• February 28, 1917. 
Canada 
Geological Survey 
Museum Bulletin No. 26. 
BIOLOGICAL SERIES, No. 6. 
Flora of Canada . 1 
By J. M. Macoun and M. O. Malte. 
In order to understand the general characteristics of the Canadian 
flora as we see it to-day, and to make clear and explain certain features 
in the distribution of a number of species and genera, which at first may 
seem perplexing or even inexplicable, we must go back to the time when 
most of the Dominion was a vast glacial waste, destitute of plant life. 
It is well known that the whole of Canada east of the Rocky Moun- 
tains was at a geologically recent period covered with glacial ice, which 
slowly advanced from the north and reached as far south as lat. 36°-37° 
in Eastern North America and lat. 46° on the Pacific coast. Evidences 
of general glaciation are also seen in the Rocky Mountains in the form of 
erratic boulders, carried there by the ice from the far north. 
As the front of the continental glacier advanced southward, the 
plants in its vicinity, which naturally were of an arctic type, were driven 
slowly towards the south. At the same time the existing vegetation 
in front of the glacier, being unable to survive under arctic conditions, 
was also forced to move southward and to cede the ground to the invading 
arctic types. When the cold reached its maximum, those parts of the 
United States which now are temperate thus had a typical arctic flora, 
i.e.y a flora almost identical with the circumpolar flora of the present time. 
With the return of a warmer climate, the arctic plants gradually retreated 
northward, followed by more temperate and southern types. Generally 
speaking, the Canadian plants can therefore all be looked upon as 
immigrants gradually taking possession of the country after the glacial 
i Reprint from Canada Year Book, 1915, Census and Statistics Office, Ottawa, Canada, pp. 43-55. 
