384 



In the autumn of 1895 collections were made in the north- 

 ern arm of the area marked as open water on Plate II., and 

 occupied at that time by a considerable amount of submerged 

 and floating vegetation, largely of Nymphcea. During high 

 water, when landmarks were submerged, this location was ap- 

 proximated as nearly as possible, but in the following spring 

 the location of the plankton station was shifted to the lower 

 arm of this open area (PI. II.), and as the vegetation emerged 

 and blocked access the station was moved to the head of the 

 slough in effluent waters. These changes in method and loca- 

 tion impair somewhat the value of this series of collections for 

 comparisons inter se, but they still serve to throw important 

 and significant light upon the relationship of such marshes and 

 of their vegetation to plankton production in their own con- 

 fines and in the channel waters to which they may contribute. 



There are 38 collections, extending continuously over 22 

 months in 1895-1897, with an interval of collection in the 

 greater part of 1896 sufficiently short to enable us to follow the 

 course of production. The scattered collections of the remain- 

 der of the period and the six additional collections in 1898 

 throw but little light upon the movement in production, 

 though they are of interest for comparison with other locali- 

 ties. 



PLANKTON PRODUCTION. 



1895. 

 (Table VII., PI. XXXIII.) 



There are but four collections in this year, in October-De- 

 cember, averaging 20.45 cm. 3 per m. 3 and having a maximum of 

 57.76 on Oct. 17, and declining to 6.38 on Dec. 19. This period 

 was one of no marked changes in the hydrographic conditions. 

 The lowered temperature and autumn rains had checked evap- 

 oration and brought about a slight increase in the volume of 

 water, as shown by the increase in depth from .25 to .45 m. The 

 lake was choked with decaying vegetation, the product of two 



