approximately 1620 sq. mi. of Wisconsin are water, as compared 

 with 55,256 sq. mi. of land surface. The suitability for algae of this 

 entire lake region is reflected in its rich and heterogeneous aquatic 

 flora. 



The great variety of aquatic habitats makes it possible to relate 

 certain species or complexes of species to what may be called 'types' 

 of lakes. In making such a correlation it is of course necessary to rec- 

 ognize that it is practically impossible to 'type' a lake, because each 

 one, in final analysis, possesses a distinct individuality. It is possible, 

 however, to classify lakes according to certain characteristics which 

 are of known biological significance. Most lakes in the region are of 

 glacial origin, but because geographical and geological features 

 (and the geological history ) are not uniform there are some general 

 differences to be noted in the bodies of water occupying respective 

 sections. For the surface features and geology of Michigan the 

 reader is referred to Leverett ( 1911, 1917). 



The pertinent geological features of Wisconsin have been ade- 

 quately described by G. M. Smith ( 1920), and the reader is urged to 

 refer to the highly informative introduction to his volume, "Phyto- 

 plankton of the Inland Lakes of Wisconsin, Part I." In this connec- 

 tion also see the remarks on p. 8 et seq., of this volume. 



SOIL TYPES AND ALGAL DISTRIBUTION 

 Michigan 



The physiography within the political boundaries of Michigan is 

 extremely varied and is in part complicated by the differences in the 

 geology of the Upper and Lower Peninsulas. The Upper Peninsula, 

 lying between Lake Superior on the north and Lake Michigan on the 

 south, is about 300 miles long, east and west, and averages about 50 

 miles in width. The Upper Peninsula itself has two definite areas 

 the character of which is determined by the type of underlying rock 

 formation. One, west of a north-south line passing through Mar- 

 quette, is a highland region which continues on over into northern 

 Wisconsin (to be discussed below), where it is referred to as the High- 

 land Lake Region. This is underlain by ancient rock formations (Pro- 

 terozoic) which are covered in most places by glacial drift; notable 

 exceptions, of course, are the Porcupine Mountains in the far 

 western part of the Upper Peninsula, and hard 'knobs' also project 

 elsewhere. The basic rock is both sedimentary and igneous. These 

 crystalline masses seem to have exerted an influence on water 

 chemistry in certain sections of this western half of the Peninsula, 

 especially in those sections where the rock is exposed or covered 



[5] 



