i ale 
1905] WHITFORD-—FORESTS OF FLATHEAD VALLEY 1OL 
tions.” Jig. z will also illustrate these smaller groups. In the 
foreground may be seen a pond which contains its characteristic 
plants; to the right of this a meadow; and between the pond and 
Flathead Lake a local prairie. These are in the forest formation. 
While the soil factors determine primarily the variety of the plant 
landscape, other factors must be taken into consideration. In this 
paper, however, the convenient term “‘edaphic formation”’ will be 
used. 
CowLes* was the first to show clearly that plant societies are 
not static, but dynamic. In brief, his contention is that the plant 
society changes with the physiographic changes that are constantly 
going on. In a former papers I have attempted to correlate the 
various plant societies found in northern Michigan. In that study 
it is shown that the region lies in a deciduous forest formation, and 
that while the coniferous forest societies are present in the more 
xerophytic conditions, there is a tendency for them to be replaced 
by the climax society, the beech-maple combination. The present 
study, made in a region with a somewhat different climate, was 
undertaken to determine whether the various plant societies could 
be correlated in the same way. For this purpose a general survey 
was made of the Flathead valley, and a portion of it was selected to 
study in closer detail. No attempt was made to study the con- 
ditions in the higher altitudes where a different climate prevails. 
PHYSIOGRAPHY.° 
There exists a close relation between the development of the 
physiography of a region and the life history of its forest formation; 
ence the necessity of describing the topographic features of the 
Flathead valley. It is a well-defined physiographic unit, situated 
in the northwestern part of Montana, about long. 114° 30’ W. and 
lat. 47° 30’-49° N. (fig. 2). The altitude of the valley is approxi- 
For a discussion of the subject, see Cowes, H. C., The physiographic ecology 
of Chicago and vicinity. Bor. GAZETTE 31:74-76. rgot. 
4 Loc. cit. pp. 75-108, 145-182. 
5 WHITFORD, H. N., The ie development of the forests of northern Michigan. 
Bor. Gazette 31: 289-325.. 
6 See ELrop, M. J., The ty siography of the Flathead Lake region. University 
of Montana Bull. 17: 197-20 
