Phytogeographical notes on the Rocky Mountain region 
Vill. Distribution of the Montane plants 
P. A. RYDBERG 
The Montane Zone or Pine Belt of the Rocky Mountain region 
includes approximately the areas between the altitudes of 2,500 
and 3,000 m. in southern Colorado, between 1,800 and 2,500 m. 
in southern Montana, and between 1,200 and 1,800 m. in Alberta, 
where the Canadian Pacific Railroad crosses the mountains. A 
general description of the Zone has been given in a previous ar- 
ticle.* 
The Subalpine Zone of the Rockies comes in contact with the 
Hudsonian or Eastern Subarctic Zone along the foothills of the 
Rockies from the headwaters of the Peace River northward, and 
here the species of the East and of the Rockies more or less in- 
termingle. But the relation between the Montane Zone of the 
Rockies and the Canadian or Eastern Boreal Zone is very different, - 
for the latter, in its typical development, reaches its western limits 
in the region of the Lake of the Woods and Lake Winnipeg. 
The most representative species of the Canadian Zone, Strobus 
Strobus and Pinus resinosa, reach their northwestern limits in this 
region and it is only in the transition belt between the Canadian 
and Hudsonian Zones, which extends along the height of land 
between the Saskatchewan and Athabasca Rivers, that species of 
the Canadian Zone range farther west. This transition belt is 
characterized by mixed woods of Pinus Banksiana, belonging to 
the Canadian, and of spruces and larches belonging to the Hud- 
sonian Zone. North of the upper Athabasca River and Beaver 
River practically the whole country is Hudsonian, while south of 
the northern branch of the Saskatchewan the prairies and the 
plains begin. These latter grassland formations belong to the 
Transition or Sub-boreal Zone. 
The number of plants common to the Canadian Zone of the 
East and the Montane Zone of the Rockies is small, outside of 
* See Bull. Torrey Club 42: 11-25. I915.- 
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