74 THE LIFE OF DEVILS LAKE 



coiiuts, which shf)W that t]ie distribution of the gcnns follows rather 

 closely that of Navienla. It occurs rarely in winter and has 

 one or two rather definite maxima in May and June. Its irregular 

 occurrence, especially in the shore collections, renders it impossible 

 to make any statements regarding maxima at other times. It some- 

 times appears in the shore collections in large numbers.* 



Cystopleura. There are six species of Cystopleura in the com- 

 plex, argus, gibba, ocellata, sorex, ventricosa and zebra, of which 

 gibba is common and the others rare. It appears erratically in the 

 plancton samples and is usuall.y too infrequent to justify any 

 conclusions regarding its seasonal distribution. Occasionally, how- 

 ever, it appears in large numbers (80 per c. c. surface Creel Bay, 

 8/10/14). 



Eunotia lunaris. There is but one record of this species for 

 the complex (Main Lake, 6/27/14). 



Sphinctocystis Uhrilis. There is but a single record of this 

 species in the complex (Main Lake, 8/28/13). 



FUNGI 



Spores of a mold occasionally occur in the plancton collections, 

 but are probabl}' accidental. 



SPERMATOPHYTA 



The only flowering plant of importance in Devils Lake is 

 the ditch grass (Ruppia maritima) but in periods of high water 

 sedges (Cyperus sp.) may occasionally be found in shallow places 

 close to shore. 



The Ruppia probabl.y plays a more important role in the life 

 of the lake than any other organism. It has already (p. 33) been 

 mentioned as characterizing one of the life zones of the lake, 

 which derives its name from this plant. It not only functions in 

 the interchange of chemical substances in the water, but con- 

 tributes a considerable part of the annual deposit of ooze on the 

 lake floor. It also furnishes shelter and attachment for many 

 smaller animals and plants. It is widely distributed, occurring in 

 most of the lakes of the complex, both brackish and fresh water. 



It grows in from 0.6 to 2.4 m. of water, forming a zone, which 

 naturally varies in width at different points, depending on the con- 

 figuration of the lake bottom. During winter much of the leafy 

 parts of the plant die. Enough of the stems survive, however, 

 to renew the growth the following year. During the break up of 

 the ice in spring considerable masses of Ruppia are carried by 

 floating ice cakes from point to point, or thrown on shore to die 



(pl. 4). 



It flowers chiefly from July to September. 



* See p. 70. 



