These plants are common in plankton and frequently appear with 

 Microcystis aeruginosa in water blooms, but they never become 

 dominant components of such blooms in our region. Most species 

 show a preference for soft water and acid habitats. 



Key to the Species 



1. Cell endophytic in the mucilage of other algae A. endophytica 



1. Cells free-living 2 



2. Cells 5-6/x in diameter, colony usually free-floating, 



sometimes attached A. rivularis 



2. Cells smaller 3 



3. Cells bright blue-green; rather crowded - A. Grevillei 



3. Cells gray-green or bluish-green, colonial mass not deeply colored; 



cells not crowded (except var. conferta of A. elachista) 4 



4. Cells 3.5^.5/x in diameter A. pulchra 



4. Cells less than S/j. in diameter — 5 



5. Cells minute, coccoid, l/x in diameter or less A. delicatissima 



5. Cells 1.5-2.5/x in diameter ___ A. elachista 



Aphanocapsa delicatissima West & West 1912, p. 431 

 PL 101, Figs. 8, 9 



Colonies spherical or elliptical, free-floating; cells minute, bluish, 

 evenly distributed throughout copious, colorless mucilage, 0.5-0.8)U, 

 in diameter. 



Common in the tychoplankton of many lakes. Most frequent in 

 soft or acid water. Mich., Wis. 



Aphanocapsa elachista West & West 1895b, p. 276 



Colonies spherical or ellipsoid,. free-floating or intermingled with 

 other algae, small and few-celled, the colonial mass pale blue-green; 

 cells small, globose, often in pairs and widely separated in colorless 

 mucilage, 1.5-2.5/x in diameter. 



Mich., Wis. 



Aphanocapsa elachista var. conferta West & West 1912, p. 432 



PI. 101, Figs. 10, 11 



Colonies ovate or globose, frequently irregular in shape (in our 

 specimens commonly very large) up to 150/i, in diameter; cells 

 spherical, crowded within a hyaline colonial mucilage, often with 

 many cells in pairs, 1.6-2.0/t in diameter. 



Euplankter. Rare to common in several soft water lakes. Mich., 

 Wis. 



[453] 



