Pool : THE VEGETATION OF THE SANDHILLS OF NEBRASKA 275 



The waters of practically all of the many ponds and lakes 

 contain considerable quantities of saline and alkaline compounds. 

 The quantitative nature of dissolved solutes in an aquatic substratum 

 has been thought to exert an important relation to the specific com- 

 position and the distribution of hydrophytic and helophytic vegeta- 

 tion. Harshberger has shown (38) that the distribution of certain 

 species of marsh plants on the New Jersey coast is governed very 

 largely by the density of the water. Much study has centered about 

 this question and much has been published (34, 50) bearing upon 

 the quantitative and qualitative aspects of the problem. 



From a mere surface view the waters of the sandhill lakes 

 appear to differ considerably in alkalinity. Some such bodies of 

 water are extremely brown and foamy. The latter nature is marked 

 under the influence of a high wind when great windrows of white 

 "suds" are blown upon the beach. Others not perhaps quite so deep- 

 colored are soapy to the skin, while still many others exhibit a 

 distinct amber color. 



It was thought that the composition and quantity of some 

 of these solutes might exert a controlling influence upon the dis- 

 tributional phenomena exhibited by the aquatic phanerogams of 

 these lakes. Samples of the water from a number of the lakes were 

 accordingly sent for analysis to the Cooperative Laboratory of the 

 United States Department of Agriculture, Bureau of Soils, at Reno, 

 Nevada. I am pleased to acknowledge my indebtedness to this 

 laboratory for certain data which they have obtained and furnished 

 me from analyses of the samples which were taken from the lakes 

 in eastern Cherry County. The following table is chosen from these 

 unpublished data. 



DISSOLVED SOLIDS IN THE WATER OF CERTAIN CHERRY 

 COUNTY LAKES 



It will be noted that the concentration is not great in any case. 

 The total amount of dissolved solids, including organic matter, is 



