897 



4-fold that in the river (.74 and 2.39), so that the run-off at this 

 season enriches channel plankton. With the exception of the 

 August collection the plankton content in the other three col- 

 lections in the lake exceeds that in the stream. The low con- 

 tent in August (l.OS) occurs at a time of lowest water, when 

 vegetation by reason both of river stage and the season is at its 

 maximum occupancy of the lake. At other times the effect of 

 the reservoir function of the lake is seen in the relatively great- 

 er production in its waters. 



The scattered data of this year are insufficient as a basis 

 for any conclusions as to the correspondence in the movement 

 of production in this and other waters. 



1895. 



(Table VIII., PI. XXXVI.) 



There are 14 collections in this year, betw^een April 10 and 

 the end of the year, averaging 9.67 cm.' per m.^ and with a 

 maximum of 61.44 on May 1 — an amplitude nearly 11 -fold that 

 of this pulse in the channel. 



The average production (9.67) is 3-fold greater than that 

 of the river in this year (3.22), and the monthly averages (see 

 table between pp. 342 and 343) are in 5 of the 9 months from 1.6- 

 to 12-fold greater in the lake than in the river. In the remain- 

 ing four months, June, July, August, and December, the ratios 

 are respectively 30.42, 9.33, 4.03, and 1.14 (river), to 9.42, 4.83, 

 3.09, and 1.00. The lower production in June-August occurs at 

 a time when, with the exception of three weeks, levels were low 

 and vegetation at its maximum occupancy of the lake, and when, 

 moreover, the current was greatly slackened in the river, and 

 channel plankton in the richly fertilized waters had more than 

 the usual time to breed, w^hile the less production in the lake 

 in December is, owing to the distribution of collections, more 

 apparent than real. 



In the matter of individual collections on coincident or 

 approximate dates the lake shows a greater plankton content 

 in 9 out of the 14 instances, and of the 9 there are 5 in which 



