69 



length of the cells in the thicker part of the filament varies 

 from about Vs of the breadth to as much as the breadth. The 

 basal cell of young filaments is elongated, and either of the 

 same thickness all over, or tapering towards the base. As the 

 plants grow older the base 

 of the basal cell is enlarged 

 into a kind of basal disc, of 

 the shape of a watch-glass, 

 turning its concave side to- 

 wards its substratum, the 

 branches of AcrosipJionia ', 

 the margin of this basal disc 

 is either entire or lobed or 

 even palmate. The disc, or 

 the discoidally enlarged base 

 of the basal cell, is very 

 distinctly marked from the 

 upper part of the basal cell. 

 The part of the basal cell 

 which is next to the disc is 

 often distinctly constricted, 

 has thick walls and narrow 

 lumen. Rhizoids are frequent, 

 both extramatrical even in 

 young plants, and intramatrical 

 especially in older plants, but 

 the filaments are not rarely 

 destitute of rhizoids. The cell 

 only contains a single, lateral 



Fig. 9. Ulothrix scutata nov. spec. 



a, b, The inferior part of two filaments 

 shoA\'ing the narrower basal portion and 

 the lower portion of the thicker superior 

 part, besides the lobed basal cell. In 

 a the filament has been removed from 

 the substratum, the discoidally widened 

 lower end of the basal cell is unilater- 

 ally developed, and we look from below 

 into the lumen of the cell, a 277 : 1 ; 

 b 667: 1. 



c, a fragment of a filament showing 

 the imperfectly divided zoosporangia. 

 422:1. 



d, a fragment showing the shape of 

 the chromatophore and the position of 

 the single pyrenoid. 422:1. 



e, a single articulation (compare the 

 text) composed of 4 cells, showing the 

 shape of the chromatophore and the 

 position of the single pyrenoid. 667 : 1. 



nucleus. The chromatophore 

 is belt-shaped and does not fill the length of the cell; 

 it contains a single lateral pyrenoid in its broader and 

 thicker end. 



I have not met with specimens with fully ripe sporangia. 



