Studies on the chemical composition of Eleocharis, Elodea, Jussiaea, Myriophyllum, Nelumbo, Potamogeton, Sagittaria, Typha, Spirogyra, Nodularia indicate that this type of vegetation is high in total N and P as compared with mesophytic plants. The total Ca content of plants growing in water was usually much higher than in native grasses and weeds on adjacent upland soil. A greater variation occurred in the percentage of Ca in different aquatic spp. than in the other elements. Differences in plant food content of the same sp. growing in different types of soil were pronounced. The superiority of certain types of aquatic vegetation in water clarification is emphasized.