with distinct, sometimes lamellate sheaths. Cells 5-10)a in diameter; 

 thallus 15-17/A wide. 



Not common in shallow water of acid lakes; among other algae in 

 tychoplankton. Mich., Wis. 



ASTEROCOCCUS Scherffel 1908, p. 762 

 Cells globose or subglobose, either solitary or in colonies of from 

 4 to 16, in colorless homogeneous envelopes of mucilage. Chloroplast 

 a stellate mass with radiate arms from a central core, which contains 



a pyrenoid. 



The shape of the chloroplast assists in differentiating this genus 

 from similarly shaped and arranged species of Gloeocystis. 



Key to the Species 

 1. Cell walls spiny - - - A. spinosus 



1. Cell walls smooth -— 2 



2. Cells solitary or in colonies of 4, 36-43ai in diameter A. superbus 



2. Cells in colonies of 8 or 16, 10-25^ in diameter --.- A. limneticus 



Asterococcus limneticus G. M. Smith 1918, p. 627 

 PL 4, Fig. 11 

 Cells spherical, arranged at some distance from one another in 

 free-floating colonies of 4-16 within a colorless homogeneous invest- 

 ing mucilage. Chloroplast stellate with 4-16 lobes radiating from a 

 central core, the lobes becoming flattened against the cell wall. Cells 

 10-25- ( 35 )/x in diameter; colonies 50-125/x in diameter. 

 Common, usually in soft water. Mich., Wis. 



Asterococcus spinosus Prescott in Prescott, 

 Silva, & Wade 1949, pp. 85, 93 

 PI. 46, Figs. 17, 18 

 Cells spherical, solitary, or 2 within a gelatinous sheath, the cell 

 wall thin and evenly beset with long, slender sharp spines. Chloro- 

 plast with numerous (more than in other species) narrow, radiating 

 strands. Cells 12-16/x in diameter. 



In shallow water of an acid lake. Mich. 



Asterococcus superbus ( Cienk. ) Scherffel 1908, p. 762 



PI. 4, Fig. 10 

 Cells spherical, solitary, or in families of 4-8 inclosed by a lamel- 

 late gelatinous envelope. Chloroplast a stellate mass with several 

 ridges or rays flattened against the cell wall. Cells 36-43/* in diam- 

 eter; 8-celled colony 93/x in diameter. 



Euplankter; tychoplankter among dense growths of miscellaneous 

 algae in shallow, soft water lakes and ponds. Mich., Wis. 



[86] 



