485 



QuiverLahe, 



Dogfish Lake, - 



Thompson Lake,- 



Phelps Lake, 



Fig. D. — Seasonal distribution of plankton production in vegetation-poor and 

 vegetation-rich waters, based on the averages of the monthly averages for all years 

 of collection. 



tioii will be found in the individual collections recorded in 

 Tables V. and IX. and VI. and VII., or in the monthly averages 

 of the table following page 342. This striking contrast is still 

 more enhanced by the statement of the monthly ratios of pro- 

 ductivity in waters rich and poor in vegetation. These range 

 from 1 to 1.5 in April to 1 to 20 in August. The fluctuations 

 in the ratio are of themselves very significant. During the 

 period from February to July inclusive the ratio is at its lowest, 

 ranging from 1 to 1.5 to 1 to 7. Excepting only the month of 

 July, this is the period of high water, in which the vegetation, 

 if present, occupies a much smaller proportion of the volume 

 of the lake, and is therefore to a proportionate degree restricted 

 in its effect upon the plankton. Under such flood conditions 

 these several localities are more or less merged in the general 



