KONGL. SV. VET. AKAUEMIENS llANDLINGAR. BAND. 20. N:<) 5. 293 



Gen. Ulva (L.) Wittr. 



Monostr. p. 9; L. Syst. Nat. Ed. 10, p. 1,346. 



Ulva crassa Kjbllm. 

 Spetsb. Thall. 2, p. 44. 

 Descr. et Fig. Ulva crassa Kjellm. 1. c. et t. 3. 



Syn. Ulva crassa Kjellm. 1. c. et Algenv. Murm. Meer. p. 51. 

 » latissima Kjellm. Vinteralgv. p, 65. 



Remark on this species. Since I have had the opportunity of examining a greater 

 number of forms of Ulva from different parts of the Scandinavian coast and especially 

 from the north coast of Norway, I have found that U. crassa is not such an indepen- 

 dent form as I believed at the time when I described it. It is nearly related to U. 

 lactuca, but it differs from that species by greater thickness, the greater height of the 

 cells, the smaller transverse diameter of the cell-rooms and by more abundant endo- 

 chrome. Until it has been fully demonstrated that these characteristics cannot be 

 employed as specific differences in the genus of Ulva, I think U. crassa ought to be 

 retained as a separate species. 



Habitat. It grows sublitoral in 3 — 5 fathoms water, attached to other algse and 

 to stones, always scattered and in sheltered localities, On the coast of Spitzbergen it 

 occurs also in winter. I found young individuals at Musselbay in November, January, 

 and April and an older specimen with zoospores on the 23 December. I have besides 

 taken specimens bearing zoospores in July and August on the coast of Spitzbergen, and 

 in July on the west coast of Novaya Zemlya. 



Geogr. Distrib. This species belongs to the arctic region of the Polar Sea, but 

 judging from one very fragmentary specimen occurs also on the north coast of Norway. 

 Greater numbers of it have not been met with anywhere. Its most northern point is 

 Musselbay on the north coast of Spitzbergen Lat. N. 79° 53'. 



Localities: The Norwegian Polar Sea: Finmarken at Oxfjord, only one incomplete 

 specimen found. 



The Greenland Sea: on the north and west coasts of Spitzbergen, rather commonly 

 dispersed, but always scarce. 



The Murman Sea: on the west coast of Novaya Zemlya local and very scarce. 



Ulva lactuca L. 

 Spec. PI. 2, p. 1163. 

 Descr. et Fig. Ulva lactuca Born, et Thur. Etucl. Phycol. p. 5 et t. 2 — 3. 



Syn. Ulva latissima Nordl. Alg. p. 40. 



» » ScHUBELEK, in Heugl. Reise, p. 317 (?). 



» linza Aresch. Phyc. Scand. p. 410 (?). 

 » 1) Klben, 1. c. (?). 



