KONGL. SV. VET. ARADEMIENS HANDLINGAB. BAND. 20. N:0 5. 303 



Murm. Meer. p. 51) that all my examinations made on specimens from different loca- 

 lities, even on those distributed by Areschoug in his Exsiccatas under the name of 

 Tetranema percursum, confirm the statements of Le Jolis and KOtzing that the plant 

 is band-shaped, elliptic in transverse section, and formed of two cells (cp. Kjellm. 1. c. 

 tab. 1, fig. 25). BoRY has already constituted a separate genus, Percursaria, for Con- 

 ferva percursa (cp. Le Jolis, Liste Alg. Cherb. p. 55). This denomination if accepted 

 would oblige us to alter the old name of the species, as the combination of Percur- 

 saria percursa is impossible. 



Swedish and arctic specimens on a more accurate comparison show rather re- 

 markable differences. The former are narrower, their cells are longer in proportion to 

 the breadth, with very thin walls while the cells are in a vegetative stage. The arctic 

 individuals are about a third thicker than the others, often branching, composed of 

 short cells with thick walls, that are square in transverse section or sometimes even 

 rectangular with the long axis in the cross direction of the frond. I propose the name 

 crassiuscula for this form. 



Habitat. This species grows in lagoons and collections of brackish water in more 

 or less considerable numbers both on exposed and sheltered coasts. I have found it 

 with zoospores at the end of June at Novaya Zemlya. 



Geogr. Distrib. It is known only from the Polar Sea north of the Atlantic. Its 

 northernmost locality is Stans Foreland in the group of Isles at Spitzbergen, about 

 Lat. N. 78°. 



Locality: The Norwegian Polar Sea: Nordlanden according to Sommerfelt and 

 specimens in Kleen's collections (f. typica). 



The Greenland Sea: the coast of Spitzbergen. 



Baffin Bay: the west coast of Greenland: Jacobshavn, Disco Isle, Whale Islands. 

 In the herbarium of the Copenhagen Museum there are found specimens without any 

 exact note of the locality. 



Gen. Prasiola (Ag.) Lagerst. 



Monogr. p. 9; Ag. Spec. Alg. 1, p. 416 ; char. mut. 



Prasiola stipitata Suhr. 



in Jess. Monogr. p. 16, sec. Lagerst. 1. c. p. 36. 

 Descr. Prasiola stipitata Lagekst. 1. c. 

 Exsicc » » WiTTR. et Noedst. Alg. exsicc. N:o 435. 



Habitat. It grows on rocks at the sea-shore. 



Locality: The Norwegian Polar Sea: Nordlanden at Lodingen according to spe- 

 cimens distributed by Foslie in Wittr. et Nordst. Alg. exsicc. under the above- 

 mentioned number. 



