— 350 — 



Monostroma (?) groenlandicum J. Ag., Rosenv. Grl. Havalg. p. 954 

 fig. 53. 



The Icelandic specimens are up to 20 cm. long, 1 mm. broad in the 

 middle of the frond and 22 — 36// thick in transverse section. My speci- 

 mens agree entirely with the exhaustive description given by Rosenvinge 

 (1. c). Fructiferous specimens have been gathered in June-July. 



This species occurs on stones and rocks in the upper part of the 

 litoral region, often gregariously and in company with Ulothrix flacca. 



In some respects (cfr. Rosenv. 1. c.) this species agrees better with 

 the genus Enteromorpha than Monostroma, and especially it seems to 

 resemble somewhat Enteromorpha aureola, in other respects it more 

 resembles Monostroma and seems thus to have an intermediate position 

 between the two genera. I follow Rosenvinge and refer it with some 

 doubt to Monostroma. 



E. I cel. common. 



N. Icel. Grfmsey (O. D.). 



NW. Icel. Dyrafjöröur (CO.); Patreksfjöröur. 



Monostroma Grevillei (Thür.) Wittr., emend. Rosenv. Grl. Havalg. 

 p. 946. 



This species occurs in the litoral region and in the upper sublitoral 

 region down to a depth of 5 fathoms. It has been collected with zoo- 

 spores in April—July, but the fructiferous specimens occurred most 

 abundantly in May and July. 



var. typica Rosenv. 1. c. ; Monostroma Grevillei Wittr., Monostr. p. 57; 

 Strömf. Algveg. p. 54 partim (e specim.). 



In younger stage of age the frond is hollow, as well known, and 

 becomes afterwards split as the plants grow older, but the hollow speci- 

 mens can occasionally attain a considerable length. I have seen fructi- 

 ferous, hollow specimens of a length of 13 cm., occurring in sheltered 

 situations. The specimens I have referred to this variety are 3 — 40 cm. 

 long and 14 — 22^ thick and the frond is more or less split, sometimes 

 quite down to the base. 



var. arctica (Wittr.) Rosenv. 1. c. ; Monostroma arcticum Wittr. Monostr. 

 p. 44 ; Monostroma latissimum Strömf. Algveg. p. 54. 



Hollow specimens of this variety can also, in sheltered situations, 

 attain a considerable length. The Icelandic specimens of this variety are 

 0,2 — 40 cm. long and 22 — 44 fi thick. The frond is usually split as in 

 var. typica. Strömfeit (1. c.) reports Monostroma latissimum from Iceland ; 

 the specimen in question however does not agree with the description of 



