96 WISCONSIN PHYTOPLANKTON 



colonial envelope and then widely divergent. Chloroplast single, cup- 

 shaped, filling practically the whole cell and generally with several pyre- 

 noids. Cells with a firm wall, one or two anterior contractile vacuoles, 

 and a single conspicuous eyespot near the base of the cilia. 



Asexual reproduction by a simultaneous division of all cells to form 

 autocolonies which are liberated by a rupture of the colonial envelope. 



Sexual reproduction heterogamous, dioecious, with all cells of a col- 

 ony developing into large immobile oospheres or plate-like masses of 

 32-64 fusiform antherozoids; or monoecious with four cells forming 

 antherozoids and the remainder oospheres. Zygote smooth-walled. 



EUDORINA ELEGANS Ehrenberg. PI. 19, Fig. 1. 



Abh. d. kgl. Ak. d. Wiss. zu Berlin 1831: 78, pi. 2, figs. KU-lOo. 1832; G. S. 

 West Brit. Freshw. Algae 194, figs. 77A-77F. 1904. 



Colonies generally 32-celled and as described above. (Facultative 

 planktont). 



Cells 12-24 p. in diam. ; colonies 50-200 /* in diam. 



Balsam (rrr), Bear (3) (ss), Bear Trap (r), Beaver dam (sss), Big Butter- 

 nut (rr), Birch (2) (ss), Birch Island (rr), Boulder (cc), Bryer (rr), Camp 

 (cc), Catherine (ss), Center (sss), Chetac (ss), Chetek (s), Clam (rr), Crawl- 

 ing Stone (rrr), Delavan (sss), Devils (1) (aa), Diamond (sss), Duck (ss), 

 Dunham (ss), Dutchmans (rrr), Elizabeth (rr), Fish (sss), Fowler (rr), 

 Granite (ss), Green (2) (rr), Grindstone (rrr), Hillman (rr), Hill (rrr), 

 Hooker (rr), Horseshoe (1) (rr), Horseshoe (2) (rrr), Howey (rrr), Island 

 (ss), Jennie (r), Kawaguesaga (rr), Kegonsa (ss), Lac Court Oreilles (rr), 

 Lac la Belle (rr), Lake of the Woods (s), Lindy (rr), Little Butternut (rr), 

 Little Wood (rrr), Long (3) (rrr), Loon (rr), Lower Nemahbin (rrr), Lower 

 Turtle (r), Lynx (rr), Meronk (rrr), Middle McKenzie (rr), Nancy (rr), 

 Nicaboyne (ss), No Mans (rr), North Turtle (ss), North Twin (rr), Number 

 One (rr), Okauchee (rr), Paddock (cc), Pine (2) (rrr), Pike (r), Pokegama 

 (2) (rr), Pokegama (3) (ss), Poplar (rr), Prairie (ss), Reserve (rr), Rain- 

 bow (rrr), Rice (1) (ss), Rooney (rr), Round (1) (r), Round (2) (rr), 

 Round (3) (sss),, Sand (1) (sss), Sand (4) (rr), Silver (2) (c), Sishebogema 

 (ss), South Crab (rr), South Turtle (sss), Spirit (sss), Squirrel (SB), Tender- 

 foot (rrr), Travis (rrr), Vermilion (rr), Waubesa (sss), White Sand (rrr). 



PLEODORINA Shaw 1894. 



Colonies always motile; spherical to sub-spherical, with 32-128 cells 

 lying some distance from one another just within the periphery of the 

 homogeneous, hyaline, gelatinous, colonial envelope and not connected 

 by cytoplasmic strands. Cells differentiated into those that are purely 

 vegetative in character and those capable of dividing to form daughter 

 colonies. All but four cells of the colony reproductive or about half 

 reproductive and half vegetative. Cells spherical to ovoid in shape. 

 Vegetative cells with a cup-shaped chloroplast containing one pyrenoid ; 



