abundant vegetation, indeed almost tropic in its 

 luxuriance. The aquatic flora of the ponds, lakes, 

 and streams of New England, of the Middle States, 

 and of the north central region is, as a rule, but 

 sparse in comparison with that which here constantly 

 meets his eyes .... he will find acres upon acres 

 of "moss", as the fishermen call it — a dense mat of 

 mingled Ceratophyllum and Elodea choking many of the 

 lakes from shore to shore, and rendering travel by 

 boat a tedious and laborious process . Beds of lotus 

 ( Nelumbo lutea ) and patches of Azolla will suggest 

 warmer climes, while the fields of rushes ( Scirpus 

 f luviatilis ) , and patches of water-lilies ( Nymphaea 

 reniformis ) , arrowleaf ( Sagittaria variabilis ) , and 

 pickerel-weed ( Pontederia cordata ) will recall 

 familiar scenes in northern waters . The carpets of 

 Lemnaceae will be surprising, and the gigantic growths 

 of the semiaquatic Polygonums will furnish evidence 

 of the fertility of their environment." 



In the same report, Kofoid (1903) provided a list of "only the 

 most common and most important members of the aquatic flora" in and 

 along the Illinois River — 48 species of emergent and submergent plants 

 comprise the list. In wider parts of the river above both Peoria and 

 Havana, there were extensive areas that were permanently occupied by 

 aquatic plants (Kofoid, 1903). As mentioned earlier, the aquatic 

 vegetation disappeared from much of the middle and upper sections of the 

 Illinois River in the 1920's, as a result of increasing pollution orig- 

 inating from Chicago. 



Improved waste treatment in Chicago apparently resulted in improved 

 conditions for aquatic plants, and between the late 1930 's and the mid- 

 1950' s, the growth was again luxuriant in Peoria Lake and elsewhere 

 along the middle section of the river (Mills, et al., 1966). 



Since the mid-1950 's, aquatic plants have again disappeared from 

 the river proper and from most backwaters and bottomland lakes which 

 are overflowed by the river (Starrett, 1972). The plants may have dis- 

 appeared from the bottomland lakes because turbidity has reduced light 

 penetration or because flocculent bottoms make anchorage against wave 

 action impossible. Starrett (1972) and Mills, et al. (1966) were of the 



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