1890 .] 
141 
[Upham. 
Tillandsia or “Spanish moss,” are left in passing from the south- 
ern to the northern states ; and instead we find in the region of the 
Laurentian lakes the bur or mossy-cup oak, the canoe and yellow 
birches, the tamarack or American larch, the black spruce, balsam 
fir, and the white, red, and Banksian pines ; while farther north 
the white spruce, beginning as a small tree in northern New Eng- 
land and on lake Superior, attains a majestic growth on the 
lower Mackenzie in a more northern latitude than a large part of 
the moss-covered Barren Grounds which reach thence eastward to 
the northern part of Hudson bay and Labrador. Thus although 
no grand topographic barrier, like a high mountain range, impass- 
able to species of the lowlands, divides this great region, yet the 
transition from a humid to an arid climate in passing westward, 
and the exchange of tropical warmth for polar cold in the journey 
from south to north, are accompanied by gradual changes of the 
flora, by which in the aggregate its aspect is almost completely 
transformed. 
In the central part of this large area, the basin of the Bed river 
of the North has been the field of my geologic exploration during 
a half dozen summers, in which careful attention has been given 
also to the geographic limits and relative abundance of both native 
and introduced plants. It has been interesting to find there the 
intermingling and the boundaries of species whose principal homes, 
or geographic range, lie respectively in the directions of the four 
cardinal points, east and west, south and north. We may conven- 
iently arrange these notes in several parts, first considering the di- 
vision of the district into forest and prairie, and the limits of spe- 
cies of trees and shrubs ; second, the herbaceous flora, including 
the flowers and grasses of the prairies ; and third, the weeds troub- 
lesome to agriculture, noting those of the eastern states and prov- 
inces winch have become equally abundant in the Red river valley, 
others of the east which are more tardily establishing themselves 
there, and especially weeds native to the country and immigrants 
from the plains, some of which are rapidly spreading eastward 
along railways, by roadsides, and in cultivated fields. 
A brief preliminary statement of the geographic position, altitude 
and contour, the diverse rocks and soils, and the climate of this 
district, will enable us to understand the circumstances which have 
controlled the development of its flora. The basin of the Red river 
