frequently 2 or 3 arise from a single cell. Cells 4-6.5/x in diameter, 

 5-8jU, long. 



Rare; on filamentous algae. Mich., Wis. 



CHAETONEMA Nowakowski 1877, p. 75 

 Thallus consisting of creeping, irregularly branched filaments of 

 cylindrical cells; branches mostly vertical from a horizontal axis, 

 ending in long, tapering, hair-forming cells; lateral walls of cells 

 also bearing a long hair, arising near tlie distal end. Parietal zonate 

 chloroplast, which covers about V2 the wall; with 1 or 2 pyrenoids. 

 This genus is confined to an epiphytic habit, occurring in the 

 mucilage of such algae as Chaetophora, Batrachospermiim, and 

 Tetraspora. 



Chaetonema irregulare Nowakowski 1877, pp. 73, 75 

 PI. 13, Figs. 6, 7 

 Characters as described for the genus. Branch-bearing cells ex- 

 tended to form the base of the branch. Cells 8-12/x in diameter, 



20-50/i long. 



Creeping in the mucilage of Tetraspora sp., Chaetophora 



incrassata, and Batrachospermum sp. 



Rare but widely distributed. Mich., Wis. 



FAMILY PROTOCOCCACEAE 



This family includes a few genera in which the thallus is a very 

 much-reduced, branching filament. The plants are usually uni- 

 cellular, but they may form clumps or expansions of considerable 

 extent on moist aerial substrates. The cells are globular, or the 

 walls may be flattened by intercellular compression. The ubiquitous 

 genus Protococcus is placed here because of the interpretation that 

 the clumps or strands of cells which are often formed in that genus 

 are essentially simple filaments; the plants occur more commonly 

 as single cells. The chloroplast is a parietal, lobed plate and 

 ulotrichaceous in character. There may be a pyrenoid. Motile re- 

 productive cells are not known, and cell division is the only method 

 of multiplication. The family is here represented by a single genus, 

 Protococcus Agardh. See Smith (1933, p. 407) for a discussion of 

 the synonymy of Protococcus and Pleurococcus Meneghini. 



PROTOCOCCUS C. A. Agardh 1824, p. 13 

 [Pleurococcus Meneghini 1837] 

 Unicellular or in indefinite clusters, the cells globose or angular 

 from mutual compression and sometimes organized to form simple 



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