404 BOTANICAL GAZETTE [DECEMBER 



4. SHRUB AND YOUNG TREE SOCIETY. Aronia arbutifolia, Ilici- 

 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. 3 



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 4 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 : 



3 See also WHITFORD, H. N., The genetic development of the forests of northern 

 Michigan. EOT. GAZ. 31:315. 1901. 



*Loc. cit., p. 150. 



