FERNS oF GLACIER PARK 99 
however, whose species are likely to have a wider distri- 
bution than those of flowering plants, are practically the 
same on both slopes, except in the case of the genus Ly- 
copodium, most of whose species are confined, apparent- 
ly, to the west slope. 
Of the life zones recognized by biologists, four are rep- 
resented in Glacier Park, as follows: 
Transition Zone. On the east slope this includes the 
plains and the narrow strips of land which extend up the 
creek valleys; also the more exposed slopes of the lower 
mountains. On the west slope the zone is represented 
by limited areas of yellow pine timber that lie along the 
North Fork of the Flathead River. The vegetation of 
the plains region consists of herbaceous plants, largely 
grasses, and of a few low shrubs. Pteridophyta are rare; 
the only ones which really belong in the zone, probably, 
are Equisetum arvense and Selaginella densa. 
Canadian Zone. This covers the largest portion of the 
Park, including all of the heavily timbered area. Open 
hillsides and meadows in the heavy timber are frequent, 
especially on the east slope. The trees are the species 
enumerated above, and there is a large representation 
of shrubby and herbaceous plants. Most of the ferns 
are found in this zone, and a large proportion of them do 
not occur elsewhere. 
Hudsonian Zone. The Hudsonian Zone is an ill-de- 
fined belt about timber line (6,000 to 7,500 feet), which 
is a transition area between the forests of the Canadian 
Zone and the meadows and barren slopes of the Arctic- 
Alpine Zone. The trees are chiefly white-bark pine and 
alpine fir. These occur mostly as low, stunted, scatter- 
ed individuals, but they are sometimes assembled in 
dense thickets. Frequently they assume the ‘‘krum- 
holz” form, The species of herbaceous plants are very 
humerous, but few are confined to this zone. Pterido- 
phyta found here are Adiantum, Cryptogramma acros- 
