XXXVlll FISHES OF ILLINOIS 



water and at low water respectively are graphically set forth by 

 Kofoid in his report on the plankton work of the Natural History 

 Survey, published in Volume VI. of the State Laboratory Bulletin. 

 "A trip by boat," he says, "across the submerged bottom-lands 

 from the Quiver shore [on the east bank, 2^ miles above Havana] 

 to the western bluff in the latter part of May would be far more 

 enlightening than any description that might be given. As we 

 leave the sandy shore of Quiver we traverse the clear, cold, and 

 spring-fed water along the eastern bank with its rapidly growing car- 

 pet of Ceratophyllum [hornwort], and in a few rods note the increas- 

 ing turbidity, rising temperature, and richer plankton of the water 

 which has moved down from the more or less open and slightly sub- 

 merged bottom to the north. As we cross the muddy bank of 

 Quiver ridge and enter the main channel of the river we find rougher 

 water, caused by the wind which usually sweeps up or down the 

 stream with considerable force between the bordering forests. The 

 water also appears much more turbid by reason of silt and plankton, 

 and no trace of vegetation is to be seen save occasional masses of 

 floating Ceratophyllum or isolated plants of Lemna, Wolffia, or Spiro- 

 dela [duckweeds]. Huge masses of cattle-yard refuse, veritable float- 

 ing gardens, may also at times be seen moving down the channel or 

 stranded in soine eddy along shore. As we plunge into the willow 

 thicket on the western shore we have to pick our way through the 

 accumulated drift lodged in the shoals or caught by the trunks of the 

 trees or the submerged underbrush. The surface of the water is 

 one mat of logs, brush, sticks, bark, and fragments of floating vege- 

 tation, with its interstices filled with Lemnacece [duckweed] dotted 

 with the black statoblasts of Plumatella. From this dark laby- 

 rinth we emerge to the muddy but quiet waters of Seeb's Lake with 

 its treacherous bottom of soft black ooze. We next enter a wider 

 stretch of more open territory with scattered willows and maples and 

 a rank growth of semiaquatic vegetation, principally Polygonums 

 [heart-weed]. The water is clearer and of a brownish tinge (from 

 the diatoms), while mats of algae adhere to the leaves and stems of 

 the emerging plants. A flock of startled water-fowl leave their 

 feeding grounds as we pass into the wide expanse of Flag Lake. 

 We push our w^ay through patches of lily-pads and beds of lotus, 

 past the submerged domes of muskrat houses built of last year's 

 rushes, and thread our way, through devious channels, among the 

 fresh green flags and rushes just emerging from the water. Open 

 patches of w^ater here and there mark the areas occupied by the 

 "moss" or Ceratophyllum, as yet at some depth below the surface. 



