colonial mucilage; cell contents with many pseudovacuoles, giving 

 a dark reddish-brown or black granular appearance to the cell and 

 making the colony opaque when viewed microscopically; colonial 

 mucilage with many radiating fibrillar concretions which clearly 

 show when the colony disintegrates with age; cells 2-3/i, wide, 3.5-6/a 

 long. 



This species is very common and occurs in abundance in suitable 

 habitats such as hard water, highly nitrogenous lakes with adequate 

 carbon dioxide content. In late summer periods these plants are 

 often conspicuous components of water blooms. Coelosphaerium 

 Naegelianum Unger is associated with Microcystis aeruginosa 

 Kuetzing emend. Elenkin, Lynghija Birgei G. M. Smith, Coelo- 

 sphaerium Kuetzingianum Naeg. and Gloeotrichia echinulata (J. E. 

 Smith) P. Richter (see C. Kuetzingianum above). When the colony 

 is disintegrating the cells and the fibrils have a distinct radiate 

 appearance and the cells seem to be at the ends of fine strands 

 from the center of the colony. 



The original description of this plant agrees with our specimens. 

 In DeToni (1907, p. 100), the name is regarded as synonymous with 

 C. Kuetzingianum Naeg. 



Coelosphaerium pallidum Lemmermann 1898d, p. 154 



PI. 106, Fig. 3 



A spherical or ovate colony of small, ovate cells crowded, but 

 evenly arranged, within the periphery of the colonial mucilage; cell 

 contents pale blue-green, without pseudovacuoles; cells l-2.5;u, in 

 diameter, 2-3.2/a long; colony 30-40/x in diameter. 



This species has smaller and more crowded cells than others in 

 our collections. These characters, together with the lack of pseudo- 

 vacuoles, are sufficient for identification. 



Rare. Found in a Sphagnum bog and in pooled streams. Wis. 



MARSSONIELLA Lemmermann 1900d, p. 275 

 A colony of 8-12 ovoid or pyriform cells, radiately arranged, with 

 their narrow ends directed outward, inclosed by a thin, transparent, 

 scarcely discernible investment (usually requiring a stain to demon- 

 strate ) . 



Marssoniella elegans Lemmermann 1900d, p. 275 

 PI. 107, Fig. 12 

 Characteristics as described for the genus; cells 1.3-5/x in diam- 

 eter, 5-6ix long. 

 Euplankter. Mich. 



[471] 



