218 The Ohio Journal of Science [Vol. XVII, No. 7, 



In addition to the records, there are some indications 

 regarding the distribution of the freshwater algae that are of 

 interest. Taken in connection with the extensive collections 

 made by the writer in central Illinois, it is very evident that as 

 one goes northward the variety and abundance of the green 

 algae decrease notably. The genera Spirogyra and Oedogonium 

 are represented by but few species north of Berrien County. 

 In Illinois the same number of collections made at corresponding 

 dates would have contained many more species. The genus 

 Microspora is poorly represented in Illinois, but increases in 

 abundance and variety in the upper part of the lower peninsula 

 and in the northern peninsula. The Blue Green Algae also 

 form an increasingly conspicuous part of the algae of the northern 

 parts of the state. 



The occurrence of Zygnema cyanospermum Cleve at 

 Manistique and Mackinaw is of interest, as this species has 

 been previously reported only from Greenland. 



The study of the distribution of algae, in both Michigan and 

 Illinois, shows that the bulk of the algae grows in pools, ditches, 

 ponds and swamps. This has an important bearing on the 

 matter of fish culture in Michigan lakes. The lakes with large 

 shallow-water areas and swampy margins are the lakes in which 

 algae are most important. Those without such margins, and 

 with sand beaches are comparatively free of algae. As the 

 algas furnish the primary food of all fishes, it is readily seen 

 that only those lakes with an abundant algal flora can ever 

 support a large number of fish. The secondary food supply 

 of fishes is made up of Crustacea; Chironomous, mosquito and 

 other insect larvae. These too depend absolutely on the alg«. 

 It is evident, therefore, that a quantitative survey of the algae 

 of a lake is a sure indication as to whether a lake is worth 

 stocking w^th fish or not. 



Lakes with rapidly sloping sand beaches are the best for 

 summer resorts because of their comparative freedom from 

 mosquitoes. They are not adapted to the growing of fish, 

 however, and it is useless for the state to stock this type of 

 lake with fish fry, as the food supply is adequate for only a 

 limited number of fish. 



