22 
Flora and Vegetation of the Churchill Area 
The 354 native species of vascular plants of the Churchill 
area are listed below, together with symbols denoting their geo- 
graphical ranges. The checklist is based upon collections made 
in the area by persons named by Scoggan (1957, p. 4). Specimens 
are filed in the herbarium of the National Museum of Canada, 
Ottawa; the Plant Research Institute of the Department of 
Agriculture, Ottawa; and the Department of Botany, University 
of Manitoba, Winnipeg. In assigning species to their respective 
subdivisions, much help has been derived from a set of distri- 
bution maps compiled by A. E. Porsild, Chief Botanist at the 
National Museum. 
The northern limits of the latitudinal subdivisions in 
Canada and Greenland are approximately as follows, due allow- 
ance being made in individual cases for local areas of warmer 
microclimates such as the upper Hamilton River basin of south- 
central Labrador (see Fig. 11 of Hare (1950)), hot spring areas 
in Alaska, and the generally less extreme fluctuations of temper- 
ature in strictly aquatic habitats: 
Low-subarctic: the northern boundary follows approximately 
the 55°F. (12.8°C.) July isotherm of mean daily temperature from 
northern Newfoundland and southern Labrador to central James 
Bay, north-central Manitoba, Great Slave Lake, Great Bear Lake, 
and southern Alaska; southernmost Greenland. 
High-subarctic: the northern boundary is taken to include 
the ranges of species more northern in distribution than the pre- 
ceding but not found in the Canadian Arctic Archipelago, except 
perhaps in southern Victoria and Banks islands and warmer micro- 
thermal areas of Baffin Island south of the Arctic Circle. In some 
areas it follows closely (in others extending considerably farther 
north of) the polar limit of tree-like conifers shown in Figure 7 of 
Hustich (1953), the Nordenskjold line shown in Hare (1951) and 
Polunin (1951), and the July isotherm of 45°F. (7.2°C.) shown in 
Chart 1—5 of Thomas (1953); West Greenland to about latitude 
70°N. and East Greenland to about latitude 65°N. (see Bocher, 
1938, Fig. 2). 
