56 



with the original description. The cromatophore usually seems 

 to fill the length of the cell, but cells containing an chromato- 



phore shorter than the cell, 

 are not rarely met with in the 

 filaments. The thickness of the 

 cell walls varies considerably, 

 according to age and growing 

 places. The thicker walls are 

 about 3//. Specimens distinctly 

 narrowed at intervals are occa- 

 sionally met with (fig. 7). 

 f. tenuior nov. f. 

 Somewhat different speci- 

 mens have been collected, grow- 



Fig. 7. Vlothrix pseudoflacca Wille. 



a, a base of a filament. 667 : 1. 



b, two cells showing the shape of the 

 single chromatophore and the posi- 

 tion of the single pyrenoid. 667 : 1. 



c, a fragment of a filament showing 

 the constriction, compare the text. 

 277 : 1. 



ing on Acrosiphonia, or loose 



between Pylaiella littoralis. 



The filaments are 7 — I4r/ thick; 



they are frequently thickest in 

 the middle and tapering towards the apex and towards the base 

 du at the base, 14// in the middle and 9/^ in the upper part). 

 The basal cell is somewhat longer than in the typical form, 

 and tapering towards the base. The upper part of the filaments 

 was fructiferous, while the lower part frequently was sterile. The 

 cells are generally longer than in the typical form, and their length 

 varies from V2 of the breadth to twice as much as the breadth. 

 Both gametangia and zoosporangia sometimes occur in the same 

 filament. The zoosporangia contain up to 8 zoospores. The 

 sporangia are frequently thicker and of a more rounded shape 

 than the sterile cells. The cell walls are usually thin, especially 

 in young filaments, and in fructiferous plants the thickness of 

 the walls does not amount to more than 1,5 /i. Generally the 

 chromatophore does not fill the length of the cell, it is usually 

 distinctly belt-shaped and contains one lateral pyrenoid in the 

 broader end. Sometimes the chromatophore seems to resemble 



