NEBKASKA WILD-DUCK FOODS. 39 



Those in "which unfavorable conditions are reflected in the charac- 

 ter of the vegetation are Big Alkali and Silver, and to a lesser extent 

 Clear Lake, and all the Garden County lakes; the others have the 

 usual abundant aquatic growth. In addition to these the collector 

 notes that Twenty-one Lake, Cherry County, is perhaps a little alka- 

 line ; however, this is not evident in the vegetation. From the char- 

 acter of the plant growth one would judge that Jones and Swan 

 Lakes, also of Garden County, are alkaline. 



The lesser injurious effects of alkalinity upon submerged vegeta- 

 tion are largely reduction of the quantity of such growth and un- 

 thriftiness of the species not adapted to withstand alkaline condi- 

 tion. The effect of still further concentration of alkalis in the water 

 is elimination of most of the species of submerged aquatic plants, 

 and the almost exclusive occupation of the water by certain resistant 

 species. Concentration beyond this point undoubtedly would have 

 a disastrous effect upon even these hardy species, but this condition 

 was not observed in any of the 44 lakes examined. 



Probably the most severe alkaline conditions of any of these lakes 

 are represented by Peterson Lake No. 2, Garden County. In this 

 lake widgeon grass {Ruq^pia occidentoilis) ^ a plant that grows in 

 brackish water, is the dominant submerged species, practically filling 

 the lake. Sago pondweed is the only other subaqueous growth. In 

 the other lakes in which aquatic plants are greatly affected by alka- 

 linity, sago pondweed in every case is the dominant and often the 

 only submerged growth. It is fortunate that such plants as these 

 endure the most alkaline waters of the sandhills, because both are 

 very important wild-duck foods, especially the sago. This pond- 

 weed also thrives in brackish water, which fact, together with the oc- 

 currence of the widgeon grass, suggests that the same qualities that 

 adapt plants for growth in salt water enable them to resist the inju- 

 rious effects of alkalis. This idea is further borne out by the char- 

 acter of the semisubmerged plants associated with the two species 

 above named in their alkaline habitat. These include saltgrass 

 {DisticMis sj)icata) and three-square {Scirpus americanus) , both of 

 which grow in coastal salt marshes. Another salt-marsh plant, 

 namely, arrow-grass {THglochin maritim-a) , while occurring at sev- 

 eral places in the sandhills, seems to have no special relation to 

 alkaline conditions. 



The species ranking next in their endurance of alkalinity, though 

 by no means to be compared with the above, are curly pondweed 

 {PotaTTiogeton yerfoliatus richardsonii) , small pondweed {Potamo- 

 geton pusillus) ^ and spike rush {Eleochar'is^ probably glaucescens) . 

 Wild rice can not endure salt, nor, presumably therefore, alkalis. 



^This species was coUected in Reno Lake also. 



