106 WISCONSIN PHTTOPLANKTON 



Farm (rrr), Prairie (c), Reserve (rr), Rice (ss), Rock (rr), Rooney (rr), 

 Rose (sss), Rozen (rr), St. Croix (rrr), Sand (3) (rrr), Shell (cc), Sishe- 

 bogema (rr), .South Turtle (rr), Spirit (r), Tamarack (sss), Tenderfoot (rr), 

 Tied Canoe (rrr), Travis (rr), Upper Nashotah (sss), Upper Nemahbin (rr), 

 Vermilion (r), Wapagossett (rrr), Waubesa (ss), White Ash (sss), Whitefish 

 (rr), White Sand (rr), Wild Goose (s), Winnebago (sss). 



DIMORPHOCOCCUS A. Braun 1855. 



Cells in groups of four and held in an irregular free-floating colony 

 by the branching remains of the old mother cell wall. Colony not en- 

 closed by a gelatinous envelope. Each aggregate of four cells lying in 

 one plane with two cells ovoid to cylindrical with rounded ends, and two 

 cells reniform to cardioid. Chloroplast of young cells single, parietal, 

 laminate, with one pyrenoid; chloroplast of old cells occupying the 

 entire cell. 



Reproduction by the division of any cell into four daughter cells 

 which remain attached to the colony by the threadlike remains of old 

 cell wall until accidentally broken away. 



DIMORPHOCOCCUS LUNATUS A. Braun. PI. 21, Fig. 5. 



Alg. Unicell. 44. 1855; Rabenhorst, Fl. Eur. Algarum 3: 36, figs, a-c (p. 6). 

 1868; G. S. West, Brit. Freshw. Algae 221, figs. 93A-93s. 1904. 



Cells of each group of four alternately arranged (in vertical view) 

 the central cells cylindrical with rounded ends, the terminal cells reni- 

 form to cardioid. (Facultative planktont). 



Cells 4-15 fji. broad, 9-25 /t long. Colonies up to 150 /* in diam. 



Bear (2) (rr), Bear (3) (rr), Beaver dam (rrr), Blue Gill (rrr), Catfish 

 (rr), Des Moines (rrr), Devils (2) (rr), Horseshoe (1) (rr), Horseshoe (2) 

 (rrr), Kegonsa (rrr), Lindy (rr), Minocqua (rrr), Mud (1) (rr), Pike (rr), 

 Pine (1) (rr), Pine Tree (rrr), St. Croix (rrr), Shell (rrr). 



WESTELLA de Wildeman 1897. 



Cells small, spherical to sub-spherical, grouped in fours (rarely 

 eights) in irregular, free-floating colonies containing 30-100 cells; the 

 colony being held together by the non-gelatinizing remains of the old 

 mother cell walls. Colonies without a gelatinous envelope. Chloro- 

 plast cup-shaped and parietal, or entirely filling the cell, with or with- 

 out a pyrenoid. 



Reproduction by the division of any cell to form 4-8 autospores that 

 remain connected with the mother colony until accidentally broken 

 away. 



