— 352 — 



landic specimens are 30—36 ^ thick (Rosenv. 1. c), the Faeroes plants 

 are 20 — 56 ii thick (Bcirgesen Faer. Alg. p. 496) and my specimens, as 

 mentioned above, 20—30 fx. The thickness of the frond is also highly 

 variable. 1 refer all my specimens to the typical form and 1 think that 

 the name var. Farlowii Fosl. ^) is superfluous. 



M. undulatum is not reported from Iceland by Stromfelt (1. c), but 

 in his collections 1 have met with specimens belonging to this species, 

 gathered by him in September in ReyOarfjorOur and EskifjorOur and 

 determined as IVI. Grevillei. 



Probably common. 



E. I eel. Rey0arfj6r9ur, EskifjorOur (Stromfelt); SeyOisfjorOur. 

 N. Icel. EyjafjorOur. 



NW. Icel. IsafjorOur, DyrafjorSur (CO.); OnundarfjorDur (Ldbk.) ; 

 PatreksfjorOur. 



SW. Icel. Reykjavik (L. K. Rosenvinge); ViOey. 

 S. Icel. Eyrarbakki, Vestmannaeyjar. 



IHonostroina fiiscum (Post, et Rupr.) Wittr., emend. Rosenv. Grl. 

 Havalg. p. 940; M. Blyttii Stromf. Algveg. p. 54. 



The Icelandic plants fully agree with the Greenlandic specimens and 

 the description and figures given by Rosenvinge (1. c). The species occurs 

 in the litoral region and is met with in the sublitoral region down to a 

 depth of 10 fathoms. Specimens collected in January and May— September 

 are fructiferous. At Reykjavik it occurred elsewhere with emptied sporangia 

 in April and on the NW. coast, at Kolbeinsa, specimens with emptied 

 sporangia occurred abundantly everywhere in September. The typical 

 specimens are 0,8 — 30 cm. (usually 8 — 30 cm,) long, 0,2 — 20 cm, (usually 

 10—20 cm.) broad and 30 — 50 // (usually 36 fjt) thick. 



f. f/randis. At low-water mark I have met with large specimens 

 lying loose on the bottom of the sea. They attain a length of 2 m. and 

 a breadth of 50 cm. and are 36 — 58// thick; they differ from the typical 

 form only by their greater size. They have two chromatophores in each 

 cell, one in each end of the cell, as the typical form (cfr, Rosenv, 1. c). 

 The specimens I have referred to this form are usually somewhat frangible 

 and destitute of the base. Besides at low-water mark I have also met 

 with this form down to a depth of 10 fathoms, but the specimens picked 

 up with the dredge were usually more or less broken in pieces. 



The typical form is common along the coast, but f. grandis has only 

 been met with in : 



^) According to F.S. Collins: The Ulvacea? of North America (Rhodora, Vol.5 

 No. 1, 1903) M. pulchruin Farl. is not identic with M. undulatum var. Far- 

 lowii Fosl., but is to be regarded as an independent species. 



