1915] 
Cahn: Ecology of Wingra Springs Region 
139 
associations, — an advanced step of the former, and a very early 
one of the latter. There are several reasons for believing this 
to be true: (1) The soil is essentially the same as that found 
in the swamp proper, with only such changes as would result 
from the fact that the land is now comparatively dry. (2) If 
earthworms may be used as an index of soil conditions, it be- 
comes evident from their absence that the soil is acid. (3) There 
Fig. 5. The Largest Spring. 
is an evident encroachment of the woods into this area, a very 
slow, though steady creeping in of the trees, as evidenced by 
the irregular character of the tree and shrub growths along 
the margin of the woods and fields. 
As typical animals we find in this association the garter 
snake, woodchuck, and meadow vole, the latter being charac- 
teristic of the areas a little removed from the woods, its place 
being taken in this area by the white-footed deer mouse. 
