56 
EIGHTH REPORT. 
the poplar-elm-osier society. This great variation in the marginal 
zone societies is due to several causes, chief among which are the fol¬ 
lowing: the variation in the ground water level in the margin; the fre¬ 
quent denuding of the margins by fire; the ease with which plants get 
into these denuded areas from the surrounding country by means of wind 
and water; and the presence of mineral matter which is washed down 
from the high ground, together with that which the larger plants may 
get by sending their roots down through the peat. 
The tamarack zone includes all those parts which are now or have 
lately been covered with tamarack or tamarack and spruce forests. At 
the present time there are, (a) the typical tamarack society, (b) the 
tamarack-spruce society, (c) the Aronia-Yaccinium society, and (d) 
the tamarack areas which have recently been denuded by fire. 
The typical tamarack society is a three-layered forest in which the 
tamaracks form the upper layer, the shrubs, such as Vaccinium corym- 
bosum, Aronia nigra, Uicioides mucronata, and Rhus vernix from the 
second, and plants such as Aralia nudicaulis, Pteridium aquilinum, 
Woodwardia Yirginica, Rubus hispidus, Uni folium Canadense, Coptis 
trifolia, and Cornus Canadensis the third. 
In the spruce-tamarack society there are about an equal number of 
each species. The spruces, however, shut out so much light that very 
few plants grow under them. 
Where man has cut away the tamaracks, the shrubs, Vaccinium 
corymbosum and Aronia nigra, make so rank a growth that nearly 
everything else is shaded out, and we find now what may be called 
a Vaccinium-Aronia society. If, however, the shrubs are cut away with 
the tamaracks, or if a spruce-tamarack society is cleared away, other 
plants get a foothold, principally those whose seeds are carried long 
distances by the wind, as Carduus, Epilobium, and Chamaenerion, or by 
birds, as Rubus and Prunus. Occasionally tamarack seedlings are 
found in these completely cleared areas. 
Where fire has denuded a tamarack area, it has usually, not only de¬ 
stroyed all the plants, but burned away the peat to a depth of from two 
inches to three or more feet. In these denuded areas Populus tremu- 
loides soon gets a foothold, then from one side, bog plants come in, and 
tamarack seedlings often get started, so that, in the course of many 
years, the tamarack society is restored. In the burned regions next to 
the margin, the bog plants are not able to compete with the plants from 
the upland, which quickly advance into the marginal zone after each 
fire. 
The Cassandra-Sphagnum zone consists chiefly of two areas, entirely 
surrounded by the tamarack zone. The plants in this zone are chiefly 
Chamaedaphne calyculata, growing in and half covored by a thick mat 
of Sphagnum. This zone has never borne tamaracks nor spruces, but 
small clumps of Vaccinium, Gaylussacia, Larix, and Picea, which ap¬ 
pear here and there, show that,'in the natural course of succession, this 
Sphagnum-Cassandra zone will be covered by a tamarack or a spruce- 
tamarack forest. 
The zone of floating plants entirely surrounds the open water. It is 
composed chiefly of sedges and the marsh fern, Dryopteris Thelypteris. 
A part of this mat is composed almost entirely of cat-tails. 
