much of which eventually forms peat because it is only partially de- 

 cayed by bacterial action. Microspora spp. are often the dominant 

 filamentous forms, attached to Chamaedaphne stems at the margin 

 of the open water. It has been observed that Oedogonium, often 

 abundant in the vegetative condition, in the open water portion of 

 acid bog lakes, rarely reproduces sexually there. In the pools and 

 ditches of the marginal mat, however, where there is a concentration 

 of organic acids and decaying matter, and where temperatures are 

 higher, fruiting plants are abundant and numerous species may be 

 identified in a single collection. Batrachospermum spp., in luxuriant 

 tufts, are also characteristic of the acid bog lake. In general it may 

 be stated that this type of lake, when shallow enough to permit opti- 

 mal temperatures, is more productive than any of the other types in 

 number of algal species. 



Alkaline Bog Lakes 



The alkaline or basic bog lake usually involves a stream meander- 

 ing through a kettlehole depression which has never been entirely 

 closed. Mud Lake, Cheboygan County, Michigan, and a small lake 

 near High Lake, Vilas County, Wisconsin, are clear examples. Al- 

 though there is an acid type of terrestrial flora forming a marginal 

 mat around such lakes, the water is fairly hard. The pH is 7.1-7.4, 

 the bound carbon dioxide is 21.8 ppm and calcium is 11.25 ppm; 

 the conductivity 85. They have, therefore, the chemistry of semi- 

 hard lakes, but the algal flora is poor both quantitatively and qual- 

 itatively. There is a conspicuous growth of Spirogyra crassa, S. 

 decemina, and Chara spp., all calcophiles (hard water organisms). 



Summary 



Some of the correlations between types of algal floras and physi- 

 cal-chemical conditions in lakes are summarized in the charts in 

 Figures 4, 5, and 6. The diagrams are based on analyses of 100 lakes 

 in Vilas and Oneida counties, Wisconsin, selected at random from 

 the list of habitats from which collections were made. The samples 

 upon which counts of algal species are based were collected during 

 July and August. The chemical data are from the records of E. A. 

 Birge and C. Juday. 



In Figure 4 the graph at the left shows the distiibution of the lakes 

 according to pH readings (expressed in number of lakes which 

 fall within the pH range indicated ) . As will be noted, the majority 

 of the lakes in the sample have a pH near 7.5. Only a few are as 

 basic as 8.3; a somewhat larger number are as acid as 5.3. Correlated 



[28] 



