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as abnormal. Each cell contains one chromatophore with a single, lateral 

 pyrenoid, and one, lateral nucleus. Regarding the shape of the chrom- 

 atophore, the structure and substance of the membrane f. geniculata fully 

 agrees with the typical var. islandica. The sporangia are usually of the 

 same shape as the sterile cells and contain about 8 zoospores. This form 

 differs essentially from the typical var. islandica by the lateral rhizoids, on 

 account of which it superficially reminds of the cell-filaments of Prasiola 

 crispa. 



var. islandica has been gathered in: 



N. Icel. Grimsey (O. D.); Arnarnes. 

 NW. Icel. Kolbeinsâ. 



f. geniculata is only known from: 

 N. Icel. Eyjafjöröur. 



Ulothrix subflaccida Wille, Studien p. 29. 



I have, in two places, met with a Ulothrix growing on Acrosiphonia 

 in the litoral region. The greatest part of my plants consisted only of 

 short, young filaments, which were attached to the filaments of Acrosi- 

 phonia with a basal cell of varying length. The basal cells were usually 

 somewhat narrower below and had occasionally somewhat expanded, 

 disciform bases. The chromatophore is a curved, parietal plate with one 

 pyrenoid and usually somewhat lobed margin, and it does not fill the cell. 

 The sporangia have the same shape as the sterile cells. Collected with 

 zoospores in June. 



E. Icel. Brimnes. 

 NW. Icel. Kolbeinsâ. 



Ulothrix pseudoflacca Wille, Studien p. 22, Tab. Il, fig. 64 — 81. 



I have in several places, on rocks at high-water mark and on litoral 

 algæ, e. g. Fucus inflatus and Rhodymenia palmata, met with specimens, 

 which seem to agree with the description given by Wille (1. c). The 

 filaments of my specimens are 12 — 22^ thick and have short cells. The 

 cells are as long as broad or up to three times broader than long. Re- 

 garding the shape of the chromatophore and the occurrence of the single 

 pyrenoid, my specimens fully agree with Wille's description. 



The specimens from E. Icel. occurred on rocks in company with 

 Monostroma groenlandicum and Urospora mirabilis, and had both zoo- 

 spores, about 8 in each sporangium, and gametes in Jane. The filaments 

 were 12 — 15 thick. The specimens on Fucus and Rhodymenia occurred 

 in company with Ulothrix flacca; they were 14 — 22 [i thick and had 

 gametes in March — April. 



