xl FISHES OF ILLINOIS 



unbroken expanse of four or more miles we find now a stream only 

 500 feet in width, while the adjacent territory is dry land save where 

 the sloughs, marshes, and lakes remain as reservoirs. Quiver Lake 

 is now much reduced in width, and it may be choked with vegeta- 

 tion except in a narrow channel where the clear water shows little or 

 no current. A half mile below we find the river water rushing in a 

 narrow "cut-oft'" across the ridge of black alluvium into the lower 

 end of the lake. The wooded banks which separate the river from 

 Quiver and Seeb's lakes are now crowded with a rank growth of 

 weeds and vines. The latter "lake" is reduced to a shallow stag- 

 nant arm of the river, whose warm turbid waters are foul with dead 

 mollusks, and whose reeking mud-flats beneath the August sun 

 shine green and red with a scum of Euglena. As we pick our way 

 through the tangle of rank vegetation we come upon Flag Lake, now 

 a sea of rushes. The discharge from this marsh to the river ceased 

 in the early summer, and its margins are even now dry, with gap- 

 ing cracks. Beyond the marsh we pass to the shore of Thompson's 

 Lake to find its southern end choked with vegetation, though the 

 greater part to the north is open water. The woodland and open 

 ground to the south are now pastures and fields of waving corn. 

 The only outlet to this large body of water, now somewhat reduced 

 in area but warm, turbid, and rich in plankton, is a tortuous slough 

 six miles to the north. The discharge, however, is in any case but 

 slight, the lake being, indeed, not infrequently the recipient of river 

 water. Spoon River still pours a sluggish but constant stream into 

 the river, but save for a waterbloom of livid green (Euglena) its 

 waters yield but little plankton. Thus, of all the wide area contrib- 

 uting to the plankton of the channel at high water there now remain 

 only Thompson's and Quiver lakes and Spoon River, each much 

 diminished in volume, but all diversified in character. 



" Returning now to the river itself we find a gently sloping bank 

 of black mud, baked and cracked by the sun's heat, extending 

 towards the softer deposit at the water's margin. A low growth of 

 grasses, sedges, and weeds springs up as the water recedes. The 

 river margin does not often have much aquatic vegetation. In 

 low-water years, such as 1894 and 1895, a considerable fringe is 

 formed along the shore, but this is quickly cleaned out on the sein- 

 ing grounds, which occupy a large part of the shore, as soon as the 

 fishing season opens in July. In years of normal high-water the 

 vegetation rarely gets much of a foothold along the shores, even at 

 low-water stages. Save for the few sandy banks where springs 

 abound, such as those below Havana along the eastern blufi", there 



