1905] WHITFORD—FORESTS OF FLATHEAD VALLEY , 199 
cottonwood, and aspen; and here and there are found small patches 
or single specimens of the western larch, Engelmann spruce, Douglas 
spruce, and bull pine. None of these were noticed on the delta 
proper, and with the exception of the Engelmann spruce they seldom 
occupy the areas that are often submerged. Of course in the lowest 
places the meadow type of vegetation prevails, and elements of it 
are scattered more or less through the area occupied by the trees. 
As already shown, the lake formerly extended over the valley north 
of it, and as its waters receded it is very probable that vegetation 
similar to that found around its shores today occupied similar areas 
around the shore line of the former lake. Of course as the gradual 
lowering of the underground water level brings about unfavorable 
conditions for those plants that exist around the shores, these are 
replaced by those needing other conditions. On that portion of the 
shore line that borders the area where the rainfall is insufficient to 
support trees, the swampy areas will pass through the meadow, the 
cottonwood-birch-aspen type, to the prairie. However, if the shore 
line be in a region that has sufficient rainfall to support a forest, the 
first two, stages will be followed by a western larch-Douglas spruce- 
bull pine stage. 
Since the Engelmann spruce is the most prevalent and the most 
important tree in the formation just described, its sylvicultural habits 
will be summarized. It has been shown that it does best in soils 
where the underground water level is not far below the surface, that 
is, for the plot under consideration, in low-lying lands bordering 
lakes, ponds, or streams. Thus it occurs not only in Swan valley, 
but also along the banks of Flathead River, where it is somewhat 
sparingly mixed with cottonwood-birch-aspen groups. It is the first 
tree to advance into the meadows. However, the Engelmann spruce 
is not confined to the more or less swampy region, for it is found 
scattered through the mesophytic areas in Swan valley. In the 
stands that lie adjacent to the spruce forests it is almost always pres- 
ent, and in some places it extends well out into the drier parts of the 
western larch-Douglas spruce formation, being found beyond the 
limits of the silver pine and lowland fir, and having a wider life range 
than either of these two species. It was often observed in the bull 
pine-Douglas spruce association where depressions in the topog- 
