629 



Plate XLIII. 



Seasonal distribution of chemical data and plankton in Illinois River in 1895- 

 1896. Chlorine, oxygen consumed, free ammonia, albuminoid ammonia, total or- 

 ganic nitrogen, nitrites, and nitrates, in parts per million, plotted according to scales 

 specified at the left, and plankton in cm. 3 per m. 3 , according to scale at the left, in 

 the form of a continuous planktograph. The hydrograph, with scale at the right, 

 is plotted in the usual form as a continuous curve. The planktograph, and the chlo- 

 rine and nitrite plots are also in continuous lines, but, owing to distribution of data 

 are more angular. Nitrite scale should read o. 1 to 0.3. 



Plate XLIV. 



The same for 1897. 



The same for 1$ 



Plate XLV. 



Plate XLVI. 



The same for Spoon River (Station M), for 1896-1897. Nitrite scale should 

 read 0.1 instead of 10. 



Plate XLVII. 



The same for 1898-1899. Plankton scale at the left should read 0.1 to 0.4 in- 

 stead of 1 to 4. 



Plate XLVIII. 

 The same for Quiver Lake (Station C) for 1895 and 1897. 



Plate XLIX. 



The same for 1898-1899. 



Plate L. 



The same for Thompson's Lake for 1897, 1898, and 1899. Nitrite scale should 

 read 0.1 instead of 1. 



