and there appear to be other sandy islands in the northwestern 

 and northeastern corners of the state. The glaciated granite soils 

 lie over crystalhne rock areas both east and west of the north- 

 central sandy soil region. Too few lakes have been sampled in 

 northwestern Wisconsin to make it possible to generalize on the 

 relative quality and quantity of the algal flora. Such limnological 

 data as have been collected by Birge and Juday indicate that there 

 are fewer soft water lakes in the northwest than in the north-central 

 and eastern sections of Wisconsin. In Washburn County there is 

 an extensive sand hill area in which the lakes are characteristically 

 soft water. Here there was the expected paucity of algae, especially 

 of phytoplankton. 



An interesting situation exists in the Waupaca chain of lakes in 

 Waupaca County, where there are glaciated granite soils, but also 

 crystalline rock and sandstone, with small amounts of surface lime- 

 stone in the extreme southeast (Whitson, Geib, and Tosterud, 

 1921 ) . The glaciated granite soils extend up into the northeast sec- 

 tion of the state, and there is a great area of similar soils in the 

 northwest. Most lakes in this type of soil are soft water, with typical 

 soft water algal floras. In many of the Waupaca lakes, however, the 

 water is so exceedingly hard that lime incrustations form on stones 

 and submerged objects of all kinds. Similar conditions occur in 

 some south-central Michigan lakes. The floras are typical hard 

 water types. Chara spp., heavily incrusted with lime, abound in 

 many lakes. The explanation of these hard water lakes in the sand- 

 stone and granite soils of Waupaca County is found in the geologi- 

 cal history of the area. Among the glacial soils brought into this 

 part of the state from the east there was a considerable amount of 

 dolomite, the outwash from which is highly calcareous. Hence, 

 lakes in the Waupaca chain are characterized by hard water floras. 



A greater part of the limnological work in Wisconsin has been 

 done in the granite and sandy soil areas of the northeast and north- 

 west sections. Accordingly more attention was given the highland 

 lake areas when the present survey was made, in order to make 

 correlations possible between types of floras and physical-chemical 

 data. In the entire northern portion of the state the lakes are char- 

 acteristically soft, poor in calcium, low in half-bound carbon diox- 

 ide and nitrogen, and give pH readings on the acid side of neu- 

 trality. A soft water lake might have 9.8 mg. or less of bound 

 carbon dioxide per liter, whereas in a hard water lake there might 

 be 43 mg. or more per liter. 



It is in such soft water lakes of northern Michigan and Wisconsin 

 that finely drawn differences can be noted in algal ecology. 



[12] 



