The Nipissing flora of the Apostle Islands Region

Abstract

In Science, February 13, 1931, a fossil flora of the Nipissing Great Lakes was briefly described by the writer. As was there stated, the plant remains are preserved in the form of rather extensive peat beds submerged in Lake Superior in the vicinity of the Apostle Islands, Bayfield County, Wisconsin. The samples, sent by Prof. J. A. Merrill, of the Superior State Teachers College, were recovered from beneath fourteen feet of sand and forty feet of water about one and one-half miles west of Sand Island, Bayfield County, Wisconsin. The geological significance of this deposit has been discussed by Dr. F. B. Taylor (Science 74: 265-267, 1931.) and the formation of the peat set as contemporaneous with the original one-outlet stage of the Nipissing Great Lakes. The botanical importance of this deposit becomes evident when one reviews literature dealing with the plant life associated with the Glacial Great Lakes. Two facts stand out, particularly: that the actual knowledge of the plants occurring at this period in the history of the Great Lakes is confined to one or more species of Chara (Coleman, A. P., Toronto University Studies, Biol. Sur. No. 21; 1922), and that much hypothetical dating of the appearance of certain Atlantic Coastal Plain plants and others in the upper Great Lakes Region, has been done, based entirely upon an interpretation of their present distribution (Peattie, D. C., Rhodora 24: 57-70, 80-88; 1922., McLaughlin, W. T., Ecol. Mon. 2: 335-383; 1932, and Anderson, E., Rhodora 35: 154-160; 1933). The appearance of these Coastal Plain plants in the Great Lakes Region at an early post glacial date seems very probable, but only since the discovery of the submerged peat beds in Lake Superior is it possible to reconstruct a picture of the ecological conditions of early Glacial Lake Nipissing time and to state definitely what plants then existed in northern Wisconsin. An examination of the largest sample of peat, which is approximately eighteen inches square and four inches thick, shows that it is of a type formed in comparatively still shallow water. About one-half of the thickness of the sample is made up of organic mud, throughout which occur fragments of plant and animal tissues. This portion of the sample is evidently a deeper water deposit than the other half which contains organic tissues in greater abundance and perfection. It seems reasonable to consider the latter as the upper side, but considering the history of the region it is impossible to state definitely. The largest sample was separated arbitrarily into three horizons, and examined both macroand microscopically for fossils. The horizon con-