204 
the sum total of the averages of the nitrogenous matters (free 
ammonia, organic nitrogen, nitrites, and nitrates) and also the 
average plankton production—sets forth in brief the relative 
fertility and production of the four localities. 
Sum of averages of 
Locality. nitrogenous matters 
—parts per million. 
Average plankton— 
cm." per m.? 
Illinois River........ 3.617 1.91 
Spoon River......... 2.586 384 
Quiver Lake......... 1.456 1,62 
Thompson’s Lake.... 2.160 6.68 
There is more nitrogenous matter in the streams than in 
the lakes, but also less plankton. Nutrition for the plankton 
is present, but time for breeding, owing to the more recent or- 
igin of stream waters, has not been afforded there, while in the 
lakes, which have somewhat of a reservoir function, there is 
time for growth of the plankton, and the store of food is de- 
pleted as compared with that in the river. It is also evident 
that there are unutilized stores of food in the rivers affording 
a basis for further development of the plankton. 
The Illinois River exhibits the greatest fertility (total 
nitrogenous matters 3,617), owing largely to sewage and in- 
dustrial wastes. These matters cause the high chlorine (21.6) 
and the large amount of free ammonia (.86) and organic nitro- 
gen (1.03), while the abundant solids in solution (304.1) and the 
nitrites (.147) and nitrates (1.58) show how large a part has 
reached the last stage of decomposition. The unutilized prod- 
ucts of decomposition are without exception in the data here 
discussed greater in the waters of the channel than in the trib- 
utary or impounded reservoir waters. 
In Spoon River the solids in suspension are highest (274.3) 
and those in solution least (167.1), a condition due to the re- 
cent origin of its water and to the large amount of silt which 
it carries. The organic origin of some of this silt is shown by 
the large loss on ignition (41.9), the oxygen consumed (14.1), the 
albuminoid ammonia (.604), and the total organic nitrogen 
