by only a thin mantle of glacial deposits. In general, the lakes of the 

 region are characteristically soft or semi-hard and are poor pro- 

 ducers of phytoplankton bulk. It is well known that waters associ- 

 ated with pre-Paleozoic rock are low in calcium, are usually but 

 little mineralized, and support a predominantly desmid flora, especi- 

 ally in habitats that possess a low pH, (The symbol pH refers to the 

 relative amount of free hydrogen ions in a solution. Soft water or 

 acid lakes have a pH below the neutral point, pH 7.0, whereas hard 

 water lakes give readings above neutral, pH 7.1-9.8. ) Such algal col- 

 lections as have been made in northwest Michigan, and in the same 

 topography of northern Wisconsin, bear out this relationship. The 

 moraines and drifts of sand left by the recession of the last glacial 

 lobes are largely responsible for the numerous soft water lakes and 

 acid swamps that are especially abundant north of Michigamme, 

 in Michigan, and in upper Wisconsin. 



The phytoplankton and the desmid flora are characteristic of soft 

 water lakes in the western section, whereas in the second area, which 

 forms the eastern part of the Upper Peninsula, the flora is, in general, 

 that of semi-hard water habitats. This is in accord with the geology 

 of the area, which is underlain by younger Paleozoic rock, all sedi- 

 mentary and unmetamorphosed. The eastern section is known as the 

 Lowlands because the greatest altitude ( witli possible exceptions ) is 

 only 250 feet above lake level. Shale and limestone predominate, the 

 latter forming a tableland along the northern border of the present 

 Lake Michigan. The Lowlands swing back westward both north and 

 south of the western Highlands into Minnesota and Wisconsin. 

 There are numerous outcroppings, and the effect on water chemistiy 

 is marked, finding expression in lakes with a pH generally higher 

 than that of the western lakes. Like the western province, the eastern 

 region has been covered by glacial drift that came in with the ice 

 from northeast Canada, resulting in extensive swamps and sluggish 

 streams. Whereas there are some habitats (such as an occasional 

 acid swamp ) that develop a rich algal flora, most of the waters in tlie 

 eastern area are not good producers, and the flora is strangely poor 

 in both bulk and number of species. Many of the slow-flowing 

 streams of the area are practically barren, and such algal forms as 

 are conspicuous are cyanophycean or hard water chlorophycean 

 (Phormidium, Oscillatoria, Spirogyra, Chara). The darkly stained 

 water of the Tahquamenon River, however, is characterized by a 

 luxuriant growth of Nitella, a genus almost always confined to soft 

 water or water rich in humic acids. 



Big Spring, near Manistique, Michigan, is an interesting habitat 

 with an algal flora that seems typical of the region. The spring has 



[6] 



