No. IO.] FRESH-WATER ALG^E. 5 1 



form a flat, more or less circular plane, or are arranged as fila- 

 ments radiating from one point. The cells are oblong, more 

 or less dilated at the anterior end, and some of them bear a 

 colorless bristle fixed in a long and narrow sheath. 



The oogonium is round, on a slender neck the continua- 

 tion of the end cell of the plant. Antheridia found either on a 

 neighboring cell or on a separate thallus. The oospore rests 

 for the winter, and develops in the following spring. Asexual 

 reproduction by zoogonidia, which are larger than the anthero- 

 zoids and may be developed in any cell. 



Coleochaete Breb. Coextensive with the family. 



C. irregularis Pringsh. (?), Fig. 800. 



C. scutata Breb., Fig. 243. 



ORDER V. GEDOGONIALES. 



Thallus of simple or branched filaments, fixed. The cells 

 are uninucleate, and with a parietal, more or less anastomosing 

 chloroplast containing one or more pyrenoids. In the vegeta- 

 tive division new pieces of the cell wall are intercalated. 

 The zoogonidia are possessed of a circle of numerous cilia 

 around the anterior end. Antheridia and oogonia are present. 



FAMILY I. CEDOGONIACE.E. 



Filaments branched or unbranched, attached in early stages. 

 Cell multiplication by transverse division, shown by transverse 

 striae, usually at the end of the mother-cell. 



The oogonia are developed in a series of vegetative cells, 

 and are at first green, then orange, and finally dark red or 

 almost black. There are two kinds of male plants, dwarf and 

 elongated ; the dwarf males are attached to female plants, and 

 the elongated males are composed of a short series of cells 

 forming an independent thread. 



Asexual reproduction by zoogonidia. The entire contents 



of a cell gather in one mass, the cell wall splits near one end, 



and the mass, with a small colorless protuberance on one end 



surrounded by numerous cilia, escapes and swims away to 



form a new plant. 



Key to Genera. 



Cells long, without a laterally placed bristle. CEdogonium* 

 Cells short, with a laterally placed bristle. . . .Bulbochate* 



