THE GREEN ALGAE OF NORTH AMERICA 189 



1897, p. 10, PI. I, figs. 6-8; P. B.-A., No. 1421. Cells lenticu- 

 lar with sharp edge, about 6 p. diam., 4 p. thick, set transversely 

 in a transparent gelatinous sheath, 20-25 P- diam. Fig. 74. 

 Mass. So. .-Inicrica. 



The filaments of this species are found among various unat- 

 tached algae in quiet water. The cell wall appears to consist 

 of two equal parts, something like two soup plates set face to 

 face ; in the filament these show the edge view, the outline 

 being an oval with acuminate ends. 



4. SCHIZOMERIS Kiitzing, 1843, p. 247. 



Frond filiform, unbranched, of a single series of cells below, 

 increasing in size above, cells dividing in all directions ; repro- 

 duction by biciliate zoospores with red stigma ; asexual (?). 

 Fresh water. 



Only one species. 



S. LEIBLEINII Kiitzing, 1843, p. 247, PI. XII, fig. i ; Wolle, 

 1887, PI. CXXV. ; P. B.-A., No. 69. Frond up to 20 cm. 

 high, rather stiff, 20-25 P- diam. at base, up to 150 p. above ; 

 terete below, with more or less deep and frequent constrictions 

 above; cells 15-30 p. diam., roundish or angular, with rather 

 thick, often lamellate membrane ; zoospores formed in the upper 

 part of the frond, freed by the breaking of the cross walls, the 

 side walls dissolving later ; zoospores thus issuing from the 

 summit of the frond. Fig. 67. In quiet fresh water. Mass., 

 R. I., N. J., Pa., Fla. Europe, So. America. 



5. STICHOCOCCUS Nageli, 1848, p. 76. 



Filaments without special basal cell, slender, consisting of 

 few or many cells ; chromatophore a parietal disk or plate, not 

 covering more than half the cell wall, containing one pyrenoid. 

 Vegetative reproduction by the breaking up of the filament into 

 individual cells, which may be considered as akinetes ; asexual 

 reproduction by biciliate zoospores without stigma, formed 

 singly in a cell, escaping by a small hole in the wall, and ger- 

 minating without forming a holdfast. 



Species of Stichoccocus occur in fresh water, rarely in salt or 

 brackish water, and also in moist places not under water. The 

 smaller species of Ulothrix, with chromatophore of irregular 

 shape, are not easily distinguished from species of Stichococcus ; 

 but the biciliate spore of the latter, the absence of a basal cell, 

 and the tendency of the filaments to break up into individual 

 cells, seem to justify keeping it as a separate genus. 



