— 240 - 



and thus corresponds closely to the C. irregularis of Wille 1 ), 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. 



IUiaphidium fasciculatmn Kütz. (R. pohjmorphu m Fresen.). The form 

 observed approaches the R. Braunii Næg. v. lacustre Chodat, I.e. fig. 117, 

 but the cells are longer and thinner. 



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

 Börgesen 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 Cosmocladium 

 saxonicum De Bary is rather interesting; the colonies observed were 

 entirely like the figures by Bruno Schröder (Ber. d. Deutsch. Botan. 

 Gesellsch., XVIII, 1900, Pl. I, figs. 2, 9, etc.). 



II. Phæophyceæ. 



Mallomonas acaroides Perty {M. Ploesslii 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 with Lemmermann's 

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

 Gesellsch. XVIII, 1900, Pl. XIX). 



Stiehogloea olivacea Chodat. The cells are more rounded, and the 

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



III. Bacillariaceæ. 



I*'ragilaria virescens Ralfs. The cells are very large, 75 — 90/j long. 



IV. Myxophyceæ. 



Aphaimomeiion sp. (?). In a sample from Harsjön 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 w r ere 

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

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

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

 desmium(?) lacustre of Klebahn (Flora o. Allg. Botan. Zeit., vol. 80, 



») Wille, N. : Algologische Notizen I— VI, p. 10, Pl. I, f. 15. 



