THE FORESTS OF THE FLATHEAD VALLEY, MONTANA. 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY. 
XVII. 
Harry N. WHITFORD. 
(WITH MAP AND TWENTY-THREE FIGURES) 
[Continued from p. 122.] 
II. EDAPHIC FORMATIONS IN FLATHEAD VALLEY. 
In the previous pages an attempt was made to show why the west 
side of the valley contains a prairie formation, and the east side a 
forest formation, and why the coniferous type of forest prevails 
rather than a broad-leaved deciduous type. A plot will now be 
presented in detail to show why in the forest formation there are 
some areas altogether without trees. In order to reach definite con- 
clusions, a limited area was selected to represent the whole forest area 
of the valley. This area, comprising about 250 square kilometers, was 
mapped, and the conditions for forest growth were determined (map). 
The relation of this area to the whole valley is shown in fig. 3- It 
lies at the northeast end of Flathead Lake, and includes a portion 
of the main valley on the east side of the Flathead River at the head 
of the lake, the low end of the Mission Range of mountains, and a 
portion of Swan valley. In this area are found many types of topo- 
graphic diversity, from Flathead Lake (890™) to the highest point 
(about 1372™) in that part of the Mission Range which is included 
in the map. No detailed study was made in the higher Swan Range 
east of the valley, though some conditions of tree growth were noted 
in these mountains. As shown by the map, five distinct edaphic 
formations were found: meadow (hydrophytic), Engelmann spruce 
(meso-hydrophytic), western larch-Douglas spruce (meso phytic), 
Douglas spruce-bull pine (meso-xero phytic), and prairie (xero phytic): 
THE MEADOW FORMATIONS (HYDROPHYTIC). 
As already mentioned, Swan valley was formerly a lake, the pres- 
ent condition being only a stage in its recession. The drainage 
consists of Swan Lake, Big Fork River, and a number of sma 
cH 
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