POTAMOGETONS IN RELATION TO POND CULTURE. 285 



The Mollusca — Plaiiorbis, Limnea, and Physa — were common on all of the Pota- 

 niogetons. 



These observations on the animal life associated with the Potamogetons afford 

 an additional contribution to the biological relations of the Chironomidse, Pyralidae, 

 Leptoceridse, Hydroptilidse, and Ephydridse, groups in which one or more members 

 have been observed in their feeding operations. Of these animals it has already 

 been recorded by Reighard (1894) that the Chironomidse are an important fish food- 

 Scattered reference is made by others of the value of aquatic insect larvae in the diet 

 of fish. The fact that these insects eat the living plant tissue of the Potamogetons 

 adds greatly to the importance of these plants from an economic standpoint. 



CONCLUSION. 



In all contributions bearing on the life conditions of the Potamogetons, the promi- 

 nence of these plants in the shoal waters has been recognized, and where special effort 

 has been directed toward the study of their life relations, an economic value has been 

 ascribed to them. The present investigation affords further evidence of the economic 

 value of these plants, and contributes the results of observation and experiment on the 

 cultivation of several species. These results warrant the expenditure of additional 

 thought and effort on what purports to be one of the most important resources of our 

 lakes, ponds, and streams. 



19371°— vol 33—15 19 



