Forest Development in the Adirondacks 3” 
stratum favorable to the establishment of balsam and com- 
parison with other somewhat similar situations confirms the 
belief that a balsam swamp forest will be its natural successor. 
Such comparison would justify one in concluding that the 
entire flood plain in this region from the flats above the Grasse 
River Outing Club to the flow had at an earlier day been 
occupied by balsam swamp forest. It suffices for the present 
purpose, however, merely to re-emphasize the contrasting soil 
conditions of these two adjacent units of the Grasse River 
sand plain. 
THE SIGNIFICANCE OF SPHAGNUM 
The foregoing description of the behavior of the vegetation 
on three physiographically distinct units of the Grasse River 
sand plain serves not only to emphasize the importance of soil 
factors in determining vegetation types and sequences. It 
focuses attention especially upon the important role played 
by sphagnum mosses. It is obvious that under certain con- 
ditions-— primarily an undrained terrain—the entrance ot 
sphagnum determines the whole subsequent course of vegeta- 
tion. This we have seen in the sequence of associations in the 
sand plain bog from the open sphagnum-sedge meadow to the 
old conifer forest. Sphagnum is the dominating element in 
this entire sequence. First by reason of the lving plants, 
second by reason of the blanket of dead, undisintegrated sphag- 
num and its underlying peat. Sphagnum forms practically 
a continuous living cover over the entire bog in closed, dark 
forest as well as in the open sedge meadow. Its upward 
growth among sedges, shrubs and conifers greatly influences 
their mode of growth. 
The entrance of new plants into the associations by spores 
or seeds is conditional always upon gaining a foothold in the 
living sphagnum ground cover excepting that in the conifer 
forest stage fallen logs, stumps, and other elevations not yet 
sphagnum covered, furnish a starting place. The roots of the 
vascular plants are imbedded in the sphagnum blanket. Their 
absorption of water and mineral nutrients takes place in the 
superficial zone composed of the living sphagnum and its erect 
