KONGL. SV. VET. AKADEMIENS HANDLINGAR. 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 ArescnovG in his Exsiccatw under the name of 
Tetranema percursum, confirm the statements of Le Joris and Kirzina that the plant 
is band-shaped, elliptic in transverse section, and formed of two cells (ep. Karrie. |. ¢. 
tab. 1, fig. 25). Bory has already constituted a separate genus, Percursaria, for Con- 
ferva percursa (cp. Le Jouts, 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 
at. N. 78°. 
Locality: The Norwegian Polar Sea: Nordlanden according to SomMerreLtT and 
specimens in KLEEN’s collections (f. typica). 
The Greenland Sea: the coast of Spitzbergen. 
Bafjin 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 (Ac.) Lacerst. 
Monogr. p. 9; AG. Spec. Alg. 1, p. 416; char. mut. 
Prasiola stipitata Sunr. 
in Jess. Monogr. p. 16, sec. LaGers?. |. c. p. 36. 
Descr. Prasiola stipitata Lacerst. 1. ec. 
Eesicc » » Wirrr. et Norpst. Alg. exsicc. N:o 435. 
Habitat. It grows on rocks at the sea-shore. 
Locality: The Norwegian Polar Sea: Nordlanden at Lidingen according to spe- 
cimens distributed by Fostie in Wirrr. et Norpsr. Alg. exsice. under the above- 
mentioned number. 
