122 ILLINOIS BIOLOGICAE MONOGRAPHS {220 
EXPLANATION OF PLATE 
Fic. 39. Boneyard just below Urbana septic tank outlet. September 14, 1920. 
Fic. 40. Salt Fork canal west of Cottonwood’s road bridge. Note bare sand bars with 
stream meandering between. Bars are covered with green putrescent matter dried by the 
sun. September 14, 1920. 
Fic. 41. Salt Fork canal at entrance of small ditch from Champaign outfall pipe. Note 
sludge bank in foreground and sewage indicated by dark color of water in center of picture. 
September 14, 1920. 
