British North American Plants. 9 
small lakes with their connecting rivers—has had, no doubt, 
its influence in limiting the distribution of many species 
there. As the prairie is approached, the drier atmosphere, 
the lighter rainfall, the more prevalent winds and the lower 
temperature must also have their effect on westward range. — 
It has, however, always appeared to me that the gradual 
widening, 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 westward extension of the 
eastern trees, shrubs and herbaceous plants presently con- 
fined to the country to the east of the Lake of the Woods- 
There is much reason to believe that the forest area may 
have at one time extended westward beyond its present 
limits in this district, even on what is now treeless prairie, 
but that fires—no doubt almost entirely since the advent of 
man there—have, by their annual depredations, extended 
the prairies gradually eastward, carrying with them the 
destruction not only of the trees, but of the numerous 
smaller plants, which are dependent on or influenced by 
the vicinity of forest areas. Whether the whole prairies 
have been at one time covered with forest, may be open to 
question, but, as I have already shown in this journal, there 
is a strong probability that to forest fires, constantly recur- 
ring, may be attributed the gradual enlargement of the 
prairie area and the formation of new prairies within forest 
areas. Another visit to the Northwest Territories the past 
summer, has only confirmed this opinion. It may be objected 
that were this the case, the stumps and roots of trees should 
be found on the surface of the prairie. That they have not 
been more frequently observed is probably due to the rapid 
decay—one authority gives four years—of the stumps of 
the poplar, the almost universal tree of the prairies and the 
immediately surrounding forests. 
The brief list hereunder given, enumerates species which 
range from the Maritime Provinces or Lower St. Law- 
rence to Lake Superior on either side, or immediately west 
of it. It is merely in its relations in Canada that the name 
St. Lawrence is applied to the group. 
