Studies on Phytoplankton II — III. 



By 



C. H. Ostenfeld. 

 II. A Sample from a Lake in Iceland. 



The Icelandic botanist, Magister H. Jonsson has brought me 

 a plankton sample, collected by him in a fairly large lake in South 

 Iceland. He has given me the following notes on the lake, of which 

 he knows no name: It is lying at Heiöi in the valley Myrdalur 

 near the south coast of Iceland at c. 63° 28' Lat. N. and 18° 55' Long. 

 W.; the distance from the sea is about 4—5 km., and moderately 

 high mountains, Arnarstakkshei öi, separate the valley from the 

 coast; thej lake is only a few hundred feet above the sea. The 

 lake shores are partly stony, partly low and with sedge-vegetation ; 

 at the north shore high, clayey hills covered with some vegetation 

 occur. The plankton sample had been collected the 28 th of July 

 1901 from the shore by throwing the net (gauze Nr. 20) out in the 

 water and drawing it back; the place where Mr. Jonsson made 

 the collection, was low and gravelly and without vegetation. 



In consequence of the collecting-method used the plankton had 

 been mixed up with impurities from the lake bottom, and several 

 bottom organisms have been found, especially bottom diatoms. 

 Nevertheless the plankton forms are rather numerous as well in 

 quantity as in quality, and it seems to me to be of interest to 

 publish the result of my examination as we do not know any- 

 thing of the freshwater plankton of Iceland. 



The animals in the sample were numerous Rotatoria (Anuraea 

 cochlearis and some other forms) and some Crustaceans (Bosmina 

 sp. etc.), further the algae threads bear two Infusorians (Cothurnia 

 sp.) affixed to them. 



The main part ot the phytoplankton consists of Diatoms: 



Asterionella gracillima (Hantz.) Heib. tiynedra ulna (Nitzsch.) 

 Ehrbg. et var. longissima (W. Sm.) Brun. Fragtlaria capucina Des- 



