Studies on Phytoplankton I. 



Notes on Phytoplankton of two lakes in Eastern Norway. 



By 

 C. H. Ostenfeld. 



In the summers of 1899 and 1900 I spent my holidays in Iho 

 valley Rendalen in Eastern Norway and made a few botanical 

 observations there which I have published elsewhere^). I had also 

 an opportunity of collecting some plankton-samples from two lakes 

 in the district, viz.: Lomnsessjon and Harsjon. 



The lake „Lomn8essjon" is rather large, but I only visited 

 the northern end which is very shallow (mostly 1—2 metres) and 

 is separated from the main part of the lake by a neck of land. 

 Odtnaes. The lake is situated in the bottom of Rendalen at a 

 height of about 350 rn. above sea-level; the surrounding country 

 is woody, chiefly pine; the vegetation of the lake is rather rich, 

 consisting mainly of Batrachium peltatimi subsp. suecicum, Pota- 

 laogetoH perfoliatus and Sparganium speirocephalum'^). 



Both in 1899 and in 1900 the plankton contained for the most 

 part animals, viz. Rotatoria and Crustacea '•^), while the plants were 

 very few in number; the temperature of the surface-water was on 

 the 25*h of July 1900 16° C. As to the entire list of the species 

 of phytoplankton observed I refer to the table found below. The 

 most characteristic feature of the list is the overwhelming majority 

 of Dinohryon accompanied by several diatoms. On compai'ing the 



') Ostenfeld, C. H. : Botaniske iagttagelser fra Rendalen i det 0stlige Norge. 



— Nyt Mag. f. Naturvidenskab, Vol. 40, III, pp. 22.3-241 with plates V & VI. 



Kristiania 1902. 

 ») 1. c. p. 232. 

 ^) Of Crustacea I have recorded (1. c. p)). 2.32, 233) Hyalodaphnia, both from 



LomnEBSsjon and Harsjon, but it was a lapsus calami, as I meant Holopedmm 



(jihhermn . 



