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.'* per m.-', 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.i to 0.3. 



Plate XLIV. 



The same for 1897. 

 The same for 1898- 



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 o.i to 0.4 in- 

 stead of I 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 i. 



