366 



pounding action of the lake is most operative and its localiza- 

 tion least pronounced. The largest production, in May and 

 June, occurs when on declining flood the flow of impounded 

 bottom-land waters from the north is greatest through the lake. 

 If we omit from both records the months of May and June, 

 we find that the averages of the remaining monthly averages 

 (see table between pp. 342 and 343) are .91 and .50 respec- 

 tively for the river and the lake. Thus for ten months of the 

 year the plankton content of the latter is but five ninths of that 

 of channel waters, and during this period the immediate result 

 of the access of the run-off from Quiver Lake will be a dilution 

 and diminution of the plankton content of channel waters, due, 

 it seems, to the relatively more recent origin, from storm and 

 seepage waters, of these tributary contributions, and to the 

 greater prevalence of vegetation in the lake. Another factor 

 operative in the diminished production of the lake is relative 

 poverty in nitrogenous substances. For example, the average 

 nitrates (cf. Tables X. and XIII.) for the year in river and lake 

 are respectively .809 and .68 ; the nitrites, .121 and .029 ; the or- 

 ganic nitrogen, .92 and .569 ; the albuminoid ammonia, .431 and 

 .275 ; and the free ammonia, .95 and .138. The unutilized ni- 

 trogenous substances in the lake are, however, of sufficient pro- 

 portions to indicate the possibility of the support of a larger 

 volume of plankton if greater time for breeding were allowed. 



1899. 



(Tables V., XII.; PI. XXIX., XLIX.) 



The 7 collections in January-March average .67 cm. 3 per 

 m. 3 as compared with .41 in the river. As in the previous year, 

 the direction of movement in production is similar in the two 

 regions. For example, the January pulse in both culminates 

 on the 17th and that of February on the 14th and the 21st, while 

 the March production is at low levels in both, and the apex of 

 the pulse is not apparent in the lake records. The invasion of 

 some channel flood water with the March rise and its speedy 

 elimination may be traced in the chemical records (PL XLIX.) 



