834 ASTRID CLEVE, THE PLANKTON OF SOME LAKES IN SWEDEN. 



The Contents of the above lists can be resumed as foUows: 



During spring, the plankton of the woodland-lakes was rather 

 scanty and chiefly composed of animal organisms (crustaceans 

 and rotatorians) together with somewhat less frequent diatoms, 

 viz. a star-forming Asterionella and the band-forming Melosira te- 

 nuissima and Tabellarice. The zigzag-bands of the latter are 

 most numerous in the Iowest, flatbottomed lakes, but when ap- 

 proaching the niountains, we find that in the deeper Skalka 

 Asterionella is prevailing. Still more towards N.W., no plank- 

 ton was niore found in the upper snow-water-layers of Saggat. 

 — Dinobryon was very scarce and desmids lacked entirely. 



In auturan the plankton of those same lakes had a very 

 diflferent composition, owing to changes in the relative frequency 

 of the forms, which, however, for the most part were the same 

 as in spring. The S.E. part of Skalka still contained a not- 

 able quantity of Zooplankton and diatoms (Asterionella, Tahel- 

 larice) but Dinobryon had grown very frequent, and in the upper 

 (N.W.) part of the water-complex it was quite a ruling form. 

 At Framnäs by Skalka and in Saggat Dinobryon filled the water 

 in such abundance that it almost hid the other organisms. Only 

 very near the banks in shallow bays there appeared a larger 

 quantity of the band-forming Tabellaria^^ which are less frequent 

 in the upper layers of deeper water. 



In the beginning of July, the still partly frozen waters of 

 Virijaure held a very scanty quantity of both Zooplankton and 

 phytoplankton. The latter consisted of desmids (ßtaurastra, 

 Arthrodesmiis) and diatoms. Among the diatoms well adapted 

 floating-forms of the star-type (Asterionella, Tubellaria fenestrata 

 V. asterionelloldes) or of a kind of parachute-type (Tabellaria 

 fenestrata v. geniculata), as it seems not before observed, pre- 

 vailed. Zigzag-bands of the Tabellarim did not occur. — Dino- 

 bryon was most scanty in the cold water still mixed with ice 

 of the western bays, but gradually increased towards the warmer, 

 south-eastern part of the lake. 



