244 



bottom-land region at least, is free from vegetation — a condi- 

 tion which prevails throughout the greater part of our prairie 

 streams. 



Quiver Lake (Station C). PI. XV.-XVII. — The vegetation is a 

 very important and much more constant factor in the environ- 

 ment of Quiver Lake than it is in that of the river. In its max- 

 imum development reached in the summers of 1894 and 1895 it 

 fills (PI. XV.) the lake from shore to shore with a closely matted 

 growth, the only open places being an interrupted and tor- 

 tuous channel through which the waters of Quiver Creek (PI. 

 II.) make their way to the river. The vegetation in the body of 

 the lake consists in the main of Ceratophyllum, with an admix- 

 ture of Elodea and Potamogeton toward the margins. Along 

 the eastern shore, and toward the upper end of the lake where 

 springy shores and sandy bottom are to be found, the vegeta- 

 tion partakes more of the permanent littoral character. Here 

 rushes, sedges, arrowleaf, and the aquatic Cruciferce and Um- 

 belliferce appear among the Potamogetons and other floating- 

 plants. In the northern area, especially along its western shore, 

 where more alluvium is found, water-lilies, pickerel-weed, and 

 the lotus abound, and the Potamogetons are more abundant (PI. 

 XVII). The "wild celery" {Vallisneria spiralis) is sparingly pres- 

 ent in the channel of the eastern arm of the lake, while in the 

 tributary bottom-lands above are aquatic meadows of wild rice 

 and other water-loving grasses, rushes, and sedges. 



In years of higher water (PI. XVI.), such as the four follow- 

 ing 1895, the vegetation differs from that of low-water years 

 more in quantity than in kind. The main body of the lake and 

 a considerable portion of both arms are freed to a greater or 

 less extent from their vegetation, a border of varying width 

 remaining near the shores, and scattered clumps dotting the 

 lake here and there in the broad stretches of open water. 



Dogfish Lake (Station L). PI. XVIII.— This lake shares the 

 flora of Quiver Lake, of which it is but the northwestern arm. 

 Its vegetation is somewhat denser, having no channels travers- 

 ing its matted growth. A fringe of marsh flora along its north- 



