404 BOTANICAL GAZETTE [DECEMBER 
4. SHRUB AND YOUNG TREE SOCIETY. Aronia arbutifolia, Iici- 
oides mucronata, Rosa caroliniana, Ilex verticillata; young 
specimens of Larix laricina, Betula pumila, Picea Mariana, and 
Acer rubrum. Beneath these occur a scattering of members of 
the preceding society, together with Limnorchis hyperborea, 
Blephariglottis lacera, Gymnandeniopsis clavellata, Osmunda 
regalis, O. cinnamomea, Dryopteris spinulosa intermedia, Vac- 
cinium canadense, Epilobium lineare, E. adenocaulon, and Viola 
blanda. 
5. CONIFER sociETy. This zone is composed of mature tama- 
racks, black spruces, low birch, and swamp maples; young and 
mature Betula lutea and Tsuga canadensis; and seeding Acer 
saccharum. The undergrowth of herbs and shrubs is diminished 
to a few stragglers. This brings us to the higher ground sur- 
rounding the bog, which is occupied by the next society. 
6. CLIMAX FOREST SOCIETY. Consists of sugar maples and 
beech trees with occasional hemlocks. The undergrowth is 
sparse, consisting principally of their own seedlings. 
Going farther north into Ontario, the series of societies is not 
so long, but apparently just as definite. But we have there 
passed the northern limits of our broad-leaved mesophytic trees 
and the climax stage is reached in a mixed forest of pine, spruce, 
and fir. This same statement probably holds for the great conif- 
erous areas of Wisconsin, Minnesota, New York, northern 
Pennsylvania, and the New England states. Even so far south 
as northern Indiana, in the sand-dune region, Cowles‘ has shown 
that where the surrounding vegetation consists of pines there is 
no doubt the same order of succession. 
It appears then that where the northern conifers are dominant 
or make up an integral part of the forests, the ecological rela- 
tions of the bog societies are clear. In other words, they nor- 
mally represent one physiographic starting-point for the develop- 
ment of the great conifer forest formation. 
There remain therefore at least two questions to be solved: 
e also WHITFORD, H. N., The genetic development of the forests of northern 
Michigan. Bort. GAZ. 31:315. Ig0I. 
4Loe, cit., p. 150. 
