WISCONSIN PHJTOPLANKTON 105 



^Reproduction by the division of the cell into 2 or 4 daughter cells 

 which remain connected to the colony by the old mother cell wall that 

 divides into 2 or 4 parts to form the branching thread system connect- 

 ing the cells. Zoospores reported but their existence is very doubtful. 

 Kesting akinetes known. 



KEY TO THE SPECIES. 



Mature cells ovoid D. EHRENBERGIANUM 



Mature cells spherical D. PTOOHELLTIM 



DlCTYOSPHAERIUM EHRENBERGIANUM Nageli. PI. 20, FigS. 11-12. 

 Gatt. einz. Algen, 73, pi. 2, figs. Ea-E 1 . 1849. 



Colonies spherical to ovoid, rarely containing more than 30 cells. 

 Cells ovoid to ellipsoid when mature. Chloroplasts 1-2, parietal, lami- 

 nate, generally with a single pyrenoid. (Facultative Planktont). 



Cells- 4-7 n broad ; 6-10 /t long. 



Clear (rr), Kegonsa (rrr>. Mendota (rr). 



DICTYOSPHAERIUM PULCHELLUM Wood. PI. 20, Fig. 13 ; PI. 21, Fig. 1. 

 Smithsonian cont. to knowl. 19, No. 241: 84, pi. 10, fig. 4. 1872. 



Colonies spherical to broadly ovoid, of 4-8-16-32 or many cells lying 

 near the periphery of the hyaline, homogeneous, gelatinous envelope. 

 Cells spherical when mature, spherical to ovoid when young ; generally 

 in fours at the ends of a repeatedly branching system of threads. Chloro- 

 plast single, parietal, cup-shaped, with one pyrenoid. (Facultative 

 planktont). 



Diam. cells 3-10 /*. 



Amicoy (ss), Balsam (rrr), Bear (1) (ss), Bear (2) (r), Bettine (s), Big 

 Butternut (r), Birch (1) (r), Birch (2) (rrr), Blake (ss), Bone (r), Boulder 

 (rrr), Canteen (rr), Carson (sss), Catfish (r), Catherine (rrr), Center (r), 

 Chain (rr), Chetac (ss), Chetek (ss), Crab (s), Cranberry (rr), Crawling 

 Stone (rrr), Deer (rr), Diamond (rr), Duck (cc), Dummy (sss), Eagle (rr), 

 Elizabeth (rrr), Fishtrap (rr), Granite (ss), Grassy (rr), Grindstone (rr), 

 Half Moon (rr), High (rr), Hillman (ss), Horse (rr), Horseshoe (1) (rrr), 

 Horseshoe (2) (ss), Howey (rr), Jag (rr), Kawaguesaga (rr), Kegonsa (r), 

 Kitten (rrr), Lac Court Oreilles (ss), Lac du Flambeau (rr), Lindy (rr), 

 Little Bass (1) (rr), Little Bass (2) (rr), Little Butternut (rr), Little Crooked 

 (rrr), Little Rice (2) (sss), Little Wood (sss), Long (1) (rrr), Long (3) 

 (rrr), Loon (r), Loveless (rr), Lower Turtle (r), Lynx (rrr), Mendota (ss), 

 Mercer (rrr), Middle McKenzie (rrr), Monona (ss), Mud (2) (rr), Mudhen 

 (rr), Nagawicka (rrr), Nancy (r), Nicaboyne (rr), North Turtle (r), Ocono- 

 mowoc (r), Okauchee (rr), Old Taylors (rr), Owen (rrr), Palmer (rr), Pe- 

 waukee (rr), Pine Tree (sss), Pokegama (1) (r), Pokegama (3) (c), Poor 



