58 



part. The base of the basal cell is discshaped, with even or 

 lobed margin, and marked from the upper part of the cell by 

 a distinct constriction. The cells in the lowest part of the 

 filament are as broad as long, or three times longer than broad, 

 in the upper part their length is varying from Vs of the breadth 

 to about as much as the breadth. The chromatophore is belt- 

 shaped and contains 

 ' one lateral pyrenoid 



in its broader end; it 

 does not fill the length 

 of the cell. The single 

 nucleus has a lateral 

 position in the cell. 

 The zoosporangia con- 

 tain at least 8 spores. 



The specimens were 

 found in the littoral 

 region on species of 

 Acrasiphonia. The fil- 

 aments jut out freely 

 from the substratum ; 

 they are usually dis- 

 tinctly constricted at 

 intervals; every artic- 

 ulation (o: the space 

 between two constric- 



Fig. 8. Ulothrix scutata nov. sp. 

 a, b, two young plants with an elongated basal 



cell, 

 c, d, two young plants showing a lobed basal 



cell. 



e, a young plant with an extramatiical rhizoid. 



f, g. h, the basal portion of older filaments 

 showing the discoidally widened lower end 

 of the basal cell; in f and g the constric- 

 tions of the filaments and intramatrical 

 rhizoids may moreover be seen. 



a, b, c, d, e 168: 1; f, g, h 422: 1. ,. , ,, 



tions) usually contains 



4 cells and only sometimes more than 4 cells, that is, when 

 some of the cells or all 4 have been divided without any dis- 

 tinct new constriction. The lower part of the filament is 5 — 6/z 

 thick, and much narrower than the remaining part of the fila- 

 ment, the thickness of which varies between 9 and 16 fx. The 

 cells of the narrower, basal part of the filaments are as long 

 as broad, or up to three times longer than broad, while the 



