THE DISTRIBUTION OF BACTERIA IN LAKES 



51 



TABLE IV 



Vertical Distributiox of Periphytic Bacteria During Midsummer Stratification. 



Oligotrophic Lakes. 

 1935 



* Bacteria per square mm per day deposited upon slides. 

 t Median date of period of immersion. 



lectecl from the various observations to coin- 

 cide as far as possible with re«iard to season, 

 choosing those observations which were 

 made near August 1. Since the time of im- 

 mersion of the slides has been varied accord- 

 ing to the productivity of the lakes, the 

 time-coincidenee is only approximate. 



Lake Alexander is not thermally strati- 

 fied. The temperature difference noted in 

 the table is the greatest that has been ob- 

 served. It will be noted that bacteria were 

 too numerous to count at the very surface, 

 though the heavy coating of the slides was 

 due perhaps more to algae than to bacteria. 



TABLE V 



Vertical Distribution of Periphytic Bacteria During Midsummer Stratification. 



Dystrophic Lakes. 

 1935 



* Bacteria per square mm per day deposited upon slides, 

 t Median date of period of immersion. 



