the surface of which setae arise (often lacking). Cells loosely ar- 

 ranged in indefinite filaments, which radiate from a common center. 

 Cell walls without setae. Chloroplasts several oval bodies, parietal 

 or scattered through the cell; 1 pyrenoid in a cell. 



Pseudulvella americana (Snow) Wille 1911, p. 90 



PL 15, Fig. 6 

 (This species probably synonymous with Chaetopeltis americana, 

 below) 



Thallus pseudoparenchymatous, from 1 to 3 cells in thickness; 

 cells in radiating linear series from a common center, 8-12/;i in 

 diameter. 



Rare. Growing on cukns of Scirpus, on submerged wood, etc. Wis. 

 CHAETOPELTIS Berthold 1878, p. 215 

 (Sometimes included in Tetrasporales ) 

 Thallus a circular attached disc of rectangular or rounded cells, 

 mono- or polystromatic, forming radiating filamentous series from a 

 common center. Free walls occasionally with slender gelatinous 

 bristles. Parietal plate-like chloroplast with a pyrenoid. 



Members of this genus should be compared with species of 

 Coleochaete, in which most monostromatic species form solid discs 

 of radiating, laterally adjoined filaments composed of cells bearing 

 an entirely different type of seta ( with sheathed base ) . 



Key to the Species 



Cells 8-12/x in diameter. - - - C. americana 



Cells 15-20At in diameter -- C. orbicularis 



Chaetopeltis americana (Snow) Collins 1909, p. 289 



Thallus an attached parenchymatous or polystromatic disc of 



rectangular cells, forming irregularly radiating series from a common 



center; outer and upper cells bearing fine hairs from their free walls. 



Chloroplast with irregular margins. Cells 8-12/x in diameter, 10-20/t 



long. 



Epiphytic on filamentous algae; less common than the following 



species. Mich., Wis. 



Chaetopeltis orbicularis Berthold 1878, p. 219 

 PL 16, Fig. 6 

 Thallus a monostromatic disc of rectangular cells forming fila- 

 mentous series and radiating irregularly from a common center to 

 form a circular plate, some cells bearing 1 or 2 fine setae. Chloro- 

 plast with smooth margins. Cells 15-20/i in diameter, 15-30/t long, 

 with thick walls. 



Epiphytic on large algae and on submerged aquatics; mostly in 



acid lakes. Mich., Wis. 



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