MICHIGAN ACADEMY OF SCIENCE. 
59 
area is a zone, two hundred feet wide, of old tamaracks and spruces, 
growing upon firm brown peat nine feet deep. Almost the only plant 
here besides the Larix laricina and Picea Mariana is Vaccinium corym- 
bosum, which grows among the trees wherever the shade is not too dense. 
Beyond the tamarack-spruce society is another burned area, which is 
practically the same as the last one mentioned. The surface of these 
burned areas is even now, after eighteen years of filling by Sphagnum, 
often twelve to eighteen inches lower than the surface of the peat in 
the tamarack-spruce zone. The deepest of these burned depressions are 
often full of water for long periods so that sedges and cat-tails are 
found growing in them. 
Next to the last burned strip is another Sphagnmn-Cassandra society, 
five hundred feet across, growing over a basin twenty-five to sixty feet 
deep. Over the deepest parts the peat is very loose/ Into this society 
besides the tamaracks and the blue-berries, the spruces are also making 
their way, following the tamaracks. An observation that the spruces 
are nearly always in circular clumps led to the discovery that in many 
instances a circle of spruces surrounds a dead or dying tamarack whose 
light has been nearly all shut off by the growing spruces. In some 
places younger stages may be seen where a fringe of young spruces is 
coming up under the lower branches of a tamarack, which has already 
made considerable growth and has shaded out the Sphagnum and Cas¬ 
sandra beneath its branches. Light is the controlling factor. The 
tamaracks shade out Sphagnum and Cassandra and give the spruces an 
opportunity to get started; the spruces, if they are numerous enough, 
shade out the tamaracks and nearly everything else within the shadow 
of their branches. Other plants within this society are Sarracenia 
purpurea, Scheuchzeria palustris, Andromeda polifolia, Oxycoccus 
Oxycoccus, Eriophorum Virginicum, Blephariglottis ciliaris, Cypripe- 
dium acaule, Monotropa uniflora, etc. 
Between the last mentioned Sphagnum-Cassandra society and the 
zone of floating plants which surrounds the lake, there is a tamarack 
society, which is less than one hundred feet wide where the line 
crosses it. At this point the peat under the tamaracks is eight feet 
deep and the marl about fifteen feet. This tamarack society is a part 
of the continuous tamarack forest which entirely surrounds the float¬ 
ing mat except for short space at the southeast. 
The bog enclosed within this zone of tamaracks is nearly elliptical 
in outline, about one hundred sixty (160) rods long east and west and 
forty-five (45) rods wide at its widest part. The lake which lies somewhat 
east of the centre of the bog, is fifty-eight (58) rods long and eighteen 
(18) rods wide. The bog here is from twenty-four (24) feet to forty 
(40) feet deep, the lower sixteen to twenty-five feet being marl and the 
upper eight to fifteen feet very loose peat. The mat at the northwest 
side and at the east end of the lake is composed almost entirely of 
cat-tails; the rest of it is composed largely of sedges and marsh ferns. 
From the south and the west sides tamaracks are advancing upon the 
bog, while Sphagnum is not very abundant. On the north side young 
tamaracks are rarely found, but Sphagnum and Cassandra are advanc¬ 
ing rapidly and smothering out the other bog plants, so that a narrow 
strip on that part of the bog is a true Sphagnum-Cassandra society. 
