288 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



length vertical to the basal plane ; growth radial by division of 

 the marginal cells ; chromatophore a large disk with one pyre- 

 noid. Asexual reproduction by biciliate zoospores with red- 

 brown stigma, formed in the central cells, few in each cell, 

 escaping through an opening in the wall. Sexual reproduction 

 in distinct plants from the asexual, by biciliate gametes with 

 reddish stigma, many in a cell. Only one species. 



P. SCUTATA Reinke, 18893, p. 33, PI. XXV ; P. B.-A., No. 

 1524. Disk 1-2 mm. diam. ; cells varying much in size and 

 shape; zoospores 15 /x diam., gametes 4 p.. On Zostera and 

 various marine algae. Fig. 95. Greenland to Conn., Jamaica. 



Europe. 



15. OCHLOCHAETE Thwaites in Harvey, 1846-1851, 

 PI. CCXXVI. 



Filaments creeping, articulate, branching ; all or nearly all 

 the cells bearing each a very long, inarticulate seta, base not 

 swollen. 



O. FEROX Huber, 1892, p. 291, PL X; Rosenvinge, 1893, p. 

 931, fig. 42 ; P. B.-A., No. 1521. Filaments radiating from a 

 center, more or less closely united to form a round or somewhat 

 irregular disk ; branching lateral, occasionally a branch rising 

 above the rest and forming locally a tissue two cells thick ; cells 

 rounded or angular, up to 30 /A diam., chromatophore parietal 

 with one pyrenoid ; setae tubular, continuous with the cells ; 

 central cells enlarging to form sporangia, up to 30 p. diam., 

 which develop each 20-30 4-ciliate zoospores, developing at 

 once on coming to rest. Fig. 92. On Cladophora, Chacto- 

 morpha and Zostera. Greenland, Mass. Europe. 



O. hystrix Thwaites has been reported from Washington, 

 Setchell and Gardner, 1903, p. 219, but there is some doubt as 

 to the determination. 



16. CHAETOPELTIS Berthold, 1878, p. 215. 

 Frond a more or less rounded disk, attached by the lower sur- 

 face, gelatinous, composed of rounded cells, in more or less dis- 

 tinct radial series; cells uninucleate, with one pyrenoid, some- 

 times with long, gelatinous, hair-like prolongations from the 

 cell wall ; sexual reproduction by the- union of biciliate gametes ; 

 asexual reproduction by 4-ciliate zoospores with red stigma. 

 Fresh water. 



There is some' question as to the character of the chromato- 

 phore in this genus ; Berthold, 1878, in the original diagnosis, 

 stating that many small disk-shaped chromatophores were 



