dioxide, and high in nitrogen, cyanophycean and diatom species 

 predominate, both in number of kinds (usually), and number of 

 individuals. In the lakes which characterize tliis calcareous region, 

 blue-green algal water blooms develop during summer periods. 

 The water chemistry is reflected in the flora of the Green Bay and 

 Fox River area, where the phytoplankton is made up almost en- 

 tirely of Microcystis aeruginosa, Aphanizomenon jios-aquae, Lijng- 

 bya Birgei, Stephanodiscus niagarae Ehrenb., and Melosira spp., 

 with infrequent specimens of Pediastrum Boryanum, P. duplex, and 

 Dinobryon sertularia. The Fox and East rivers drain a calcareous 

 and clay soil region, gathering considerable quantities of waste from 

 agricultural lands and industrial plants. Williamson et al. (1939, 

 p. 66) have expressed the opinion that a heavy bloom of blue-green 

 algae in these waters is not related to the nitrogen content, but 

 nitiogen in available form for plants is relatively abundant in 

 these streams, especially as compared with that in inland lakes. 

 Bound carbon dioxide is likewise relatively abundant. Such fea- 

 tures are usually correlated with luxuriant cyanophyte-diatom 

 floras (see Sawyer, Lackey, and Lenz, 1943). In lakes that have a 

 chemistry similar to the Fox and East Rivers the number of blue- 

 green algal individuals may reach several million per liter. 



Lake Geneva, Walworth County, Wisconsin, is another hard water 

 lake ni the glaciated hmestone soil area which is larger and deeper 

 than Lauderdale Lake. It is high in carbonates (74 ppm), calcium 

 (20.7 ppm), magnesium (26.9 ppm), sodium (4.4 ppm), and HCO 

 (110.5 ppm). Analyses of Lake Geneva water samples made in 

 August 1940 show a relatively high nitrogen content: organic nitro- 

 gen 0.55 ppm, ammonia 0.01 ppm, nitrate nitrogen 0.8 ppm, nitrites 

 0.0. As might be expected, the phytoplankton of this lake is predom- 

 inantly blue-green. Microcystis aeruginosa, CoelospJmerium Naegeli- 

 anum, and Lyngbya Birgei being the most conspicuous represent- 

 atives. The green algae which occur here in June, for example, are 

 Cladophora fracta and C. glomerata, species typical of hard water 

 habitats. In contrast, the desmid and predominantly chlorophycean 

 flora appears not to occur in the lakes of this limestone region. There 

 is further discussion of hard water lakes below. 



The third and fourth soil types, which are much less clearly de- 

 fined, constitute, in general, the upper third of the state. This is 

 basically a crystalline rock area, but within it are sandy soils and 

 glaciated granite soils. The former predominate in the north-central 

 counties: Vilas,' Oneida, parts of Langlade, Lincoln, Forest, Iron, 

 and Price, The same soil appears in the central part of the state in a 

 sandstone region including Juneau, Adams, and Monroe counties, 



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