latter case flattened when seen in side view. The wall is in 2 equal 

 or unequal pieces between which a section may be interpolated to 

 bring about a lengthening of the cell. In most forms there is a spine 

 at the poles, or at the corners of the cell. Reproduction is by auto- 

 spores or, rarely, by zoospores. Centritractus^ should be compared 

 with Ophiocytium. 



Key to the Genera 



Cells furnished with a spine at either end of the 



cell, which is usually long-cyhndric- Centritractus 



Cells without spines Bumilleriopsis 



BUMILLERIOPSIS Printz 1914, p. 50 



Cells solitary or adjoined end to end to form short filaments or 

 radiating clusters; the cells ellipsoid, subcylindric, or fusiform, with 

 poles either smooth or furnished with a blunt apiculation, the two 

 poles symmetrical or unsymmetrical; cell wall thin, or thick and 

 firm, smooth, the 2 sections not clearly apparent except during 

 liberation of autospores or zoospores; chromatophores 2 to many 

 parietal plates. 



Bumilleriopsis brevis Printz 1914, p. 50 

 PI. 95, Figs. 6-8 

 Cells cylindric or subcylindric, straight or slightly curved to 

 semilunate, the poles unsymmetrical, one pole sometimes sharply 

 pointed, the other broadly rounded; chromatophores numerous par- 

 ietal discs; cells 4-10/. in diameter, 10-30-(60))a long. 

 In an acid bog lake. Mich. 



CENTRITRACTUS Lemmermann 1900d, p. 274 



Cells ellipsoid or subcylindrical, with a long or short spine at 

 each pole; wall in 2 portions, the juncture occurring either in the 

 midregion or near one end, or in elongated cells, occurring at two 

 points so that a cap' is formed at either end of the cell; chromato- 

 phores (l)-2-4-(5), yellowish-brown, plate-like bodies; reproduction 

 by autospores, aplanospores, or zoospores (Pascher 1937-1939, 



p. 849). 



Key to the Species 



Spines Vi the length of the cell or less; 



cells elliptic to oblong-elliptic C. dubtus 



Spines as long as the cell body or nearly so; cells 



cylindrical ( cylindric-ovoid when young) C. belanophorus 



•''Spelling changed to Centratractus by Pascher. 



[ 360 



