— 240 — 



and thus corresponds closely to the C. irregularis of Wille^), recorded 

 by its author from several Norwegian lakes. The differences between these 

 two species seem to be very slight, and I should think it better to regard 

 them as one species. 



Rhaphidiiim fasciculatuin Kiitz. {B. pohjmo7-phum Freseu.). The form 

 observed approaches the R. Brannii Naeg. v. lacustre Ghodat, 1. c. fig, 117, 

 but the cells are longer and thinner. 



With regard to the Desinids I have very little to remark. Mr. F. 

 Borgesen was kind enough to examine some of them, and I owe him 

 my very best thanks. The species enumerated in the table are not all 

 plankton-forms. The occurrence of a few colonies of Cosmocladiuui 

 saxonicum De Bary is rather interesting; the colonies observed were 

 entirely like the figures by Bruno Schroder (Ber. d. Deutsch. Bolan. 

 Gesellsch., XVIII, 1000, PI. I, figs. 2. 9, etc.). 



II. Phaeophycese. 



Mallomonas acaroides Perty (M. Ploesslu Perty). The specimens 

 examined had very long hairs (at least twice as long as the body), and 

 the body was sometimes prolonged at the one end, and then pyriform. 



Dinobryon divergens Imhof agrees very well witli Lemmermann's 

 figures of D. divergens and D. cylindricum Imhof (Ber. d. Deutsch. Botan. 

 Gesellsch. XVIII, 1900, PI. XIX). 



Stichogloea olivacea Ghodat. The cells are more rounded, and the 

 colonies larger than in Ghodat's figures (Bull. Herb. Boiss. 1897, Pl.X). 



III. Bacillariaceae. 



Fragiiaria virescens Ralfs. The cells are very large, 75 — 90/;! long. 



IV. Myxophycese. 



Aplianizomenon sp. (?). In a sample from Harsjon I found a blue- 

 green alga, about which I am very uncertain. It consists of many-celled 

 threads which form small bundles; neither heterocysts nor spores were 

 observed; the cells are isodiametrical, or longer than they are broad 

 (length 8—16 ij., breadth 8 //), and are barrel-formed, i. e. the threads 

 are like strings of beads (moniliform). The alga resembles the Tricho- 

 desmiuw {?) lacustre of Klebahn (Flora o. AUg. Botan. Zeit., vol. 80. 



') Wille, i\.: Algologische Notizen I-VI, p. 10, PI. L f. 15. 



