62 
EIGHTH REPORT. 
The mat seems to be advancing rapidly over the lake by growing from 
the margin and by the increase in the size and number of detached 
pieces of the mat, which have floated out and become lodged upon the 
rootstocks of Nymphaea advena. Other plants found in this floating- 
zone are Zizania aquatica, Eriophorum polystachyon, Sagittaria lati- 
folia, Comarum palustre, Menyanthes trifoliata, Decodon verticillatus, 
Salix myrtilloides, Marchantia poiymorpha, Drosera rotundifolia, etc. 
The tamarack forest on the south side is from one hundred feet to 
three hundred feet wide, and rests upon from eleven to twenty-eight 
feet of brown peat and marl. Between this tamarack forest and the 
shore is the marginal zone, which shows little evidence of having ever 
been burned over and which has no distinct marginal depression. Be¬ 
sides grasses and sedges, growing in this zone there are several low 
shrubs, Rosa Carolina, Spiraea salicifolia, Dasiphora fruticosa, etc. 
The profile through the several zones (Fig. 3) shows that the younger 
zones of floating plants and of Sphagnum and Cassandra lie over deeper 
basins which must be the last places to be filled with peat and to be 
covered with bog plants. The water plants fill the water nearly to 
the top with very loose peat, the mat grows out upon this, then tama¬ 
racks come upon the mat, either directly, as upon the south and west 
sides, or after an intervening Sphagnum-Cassandra stage, as upon the 
north side of the large basin (Fig. 2 and 3, X) and in the smaller 
basins (Y and Z). Although tamaracks may come directly upon the 
sedge mat, young spruces are first found in the Sphagnum-Cassandra 
zone. These results correspond with the results which have been obtained 
by Burns* and Pettee.f From Fig. 3, it might seem that the basin 
X should have been filled before the deeper basin Y, but Fig. 2 shows 
that X is very much larger than Y. Moreover, borings show that parts 
of X are deeper than the part through which the profile was taken. 
It is reasonable to suppose that a zone of water plants could fill the 
small basin Y in much less time than an equally wide zone could fill 
the large basin X. 
In a consideration of the burned areas, it is evident that the peat 
is seldom burned evenly or *to a uniform depth. There may be ir- 
repilar depressions, where every living thing was totally destroyed, 
lying adjacent to strips which were merely burned over and in which 
the majority of the plants were not killed. A good illustration of this 
is found in the north part of the swamp (Fig. 2, D), (Fig. 4). Along 
the margin is a common marginal society of Salix, Populus, Ulmus, 
Cornus, Solanum, Caltha, etc. In wet seasons the ground is covered 
with more or less water. There are no evidences of burns near the 
shore, but several rods from it, half burned tamarack stumps with all 
their upper roots exposed and partly burned show that fires must have 
lowered the leved at least eighteen to twenty-four inches. The plants, 
however, are in no way different here from those found near the shore. 
About fifteen rods from the shore there is a strip from one to several 
rods in width, which does not seem to have been burned out. It is 
higher than the rest of the ground so that its surface is comparatively 
dry at all seasons of the year, and upon it are suchl plants as Aralia. 
* Report Michigan Academy of Science, 1994, P, 76. 
t Report Michigan Academy of Science, 1905, P. 126. 
