(V21 



even the size gives ns the least certainty, il appears to me to be 

 impossible to maintain Cl. subpronum as species; il should be clas- 

 sified with Cl. aciculare West. I do not think either that Lemmer- 

 m an ns above-mentioned variety is justifiable, the onlv difference 

 being that il mav altain to somewhat larger dimensions. Ol' the 

 closely related forms, two more mav be mentioned, viz. Closterium 

 limneticum Lemm. which is somewhat smaller, and according to 

 Lemmermann has a fairly distinct vacuole al the apex of the 

 cell; and a form of Cl. Ceratium Perty described and figured by 

 Bruno Schroder in »Planktonflanzen ans Seen von Westpressen« 1 . 



III. MYXOPHYCEAE. 



1«}. Coelosphaerium Naegelianum Unger. 



The few individnals which have heen observed agree well with 

 O. Borge's description and (igure (Bol. Nolis., 1900, p. 5, PL I, lig. 3) 

 and with Migula's Kryptogamae Germaniae, Anstriae el Helvetiae 

 exsiccatae, Fase. 2, N. 14. Il is this form which has heen recorded 

 as C. Kutzingianum Nag. in »Freshwater Algæ«. 



Chroococcus limneticus Lemm. as well as Microcystis incerta Lemm. 

 oecur in several of the gatherings. The discoverer of the species, 

 Mr. E. Lemmermann, has had an opportunity of exainining one 

 of the samples from Sorvaagsvatn, and has fonnd these Iwo spe- 

 cies as well as M. stagnalis Lemm. in the sample; we have nol heen 

 able lo lind the latter speeies; they are recorded in »Freshwater 

 Algæ«, p. 206, under the names Polycystis incerta Lemm. and P.pal- 

 lida Lemm. 



IV. I5ACILLARIACEAE. 



(by C. H. Ostenfeld). 



The speeies recorded were all fonnd by E. Østrup except 

 Fragilaria crotonensis of which I have onlv seen 2 chains. Onlv 

 Asterionella formosa and Cyclotella radiosa are special plankton- 

 organisms, hul all the others are also fairly common in lakes 

 with low temperature, especially the Tabellarias. Strangely enough, 

 Melosira, which is otherwise an important plankton -genus, is al- 

 most totally absent. 



1 Berichte d. deutsehc bot. Gesellschaft, Vol. XVII. 1899, p. 159, pi. 10, 



lig. .'5 a, 1). 



