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 the 

 valley Rendalen in Eastern Norway and made a few botanical 

 observations there which I have published elsewhere 1 ). I had also 

 an opportunity of collecting some plankton-samples from two lakes 

 in the district, viz.: Lomnæssjon and Harsjön. 



The lake „Lomnæssjon" 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, 

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

 height of about 250 rn. above sea-level; the surrounding country 

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

 consisting mainly of Batrachium peltatum subsp. suecicum, Pota- 

 mogeton perfoliatus and Sparganium speirocephalum 2 ). 



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

 part animals, viz. Rotatoria and Crustacea 3 ), while the plants were 

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

 the 25 th of July 1900 16° G. 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 Dinobryon accompanied by several diatoms. On comparing the 



*) Ostenfeld, G. H.: Botaniske iagttagelser fra Rendalen i det østlige Norge. 

 — Nyt Mag. f. Naturvidenskab, Vol. 40, III, pp. 223-241 with plates V & VI. 

 Kristiania 1902. 



2 ) 1. c. p. 232. 



3 ) Of Crustacea I have recorded (1. c. pp. 232, 233) Hyalodaphnia, both from 

 Lomnæssjon and Harsjön, but it was a lapsus calami, as I meant Holopedium 

 gibberum. 



