WISCONSIN PHYTOPLANETON 153 



var. ALTERNANS (Eeinsch) Borge. PI. 38, Figs. 10-11. 



Arkiv. for Botanik 6, No. 1: 57. 1906. 



Bcenedesmus alternans Reinsch, Abh. Senckenb. Naturf. Ges. 6: 135, pi. 20, 

 fig. D e . 1866. 



Colonies flat, generally 8-celled, with a very marked alternate ar- 

 rangement of the component cells. Cells ovoid to elliptic. (Tycho- 

 planktont) . 



Cells 4-8 n broad, 6-15 p. long. 8-celled coenobia 12-30 /* broad, 

 22-45 ft long. 



Blake (rr), Devils (1) (rrr), Muskallonge (rr). 



Since cultural studies have shown that the alternate arrangement cf 

 cells is a constant character it is proper to consider this a distinct vari- 

 ety. The variety has also been found in lakes where the typical form 

 is absent. 



SCENEDESMUS ARCUATUS Lemmermann. PI. 38, Figs. 12-14. 

 Forschungsbr. a. d. Biol. Stat. zu Plon 7: 112, pi. 1, figs. 2-4. 1893. 



Colonies always curved, of 4-8-16 (generally 8) cells arranged in a 

 double row. Cells ovoid, sometimes angular by mutual compression 

 at the base. Coenobia with small interstices between the cells. Cell 

 wall smooth, without spines or teeth. (Euplanktont). 



Cells 3-9 (i broad, 9-17 p long. 8-celled coenobia 15-25 /* broad, 

 15-40 p. long. 



Beaverdam (rr), Blake (rrr), Camp (rrr), Center (ss), Chain (rr), 

 Cochrane (rr), Cranberry (rr), Hillman (r), Lac Court Oreilles (rr), Lac du 

 Flambeau (rr), Little Bass (2) (rr), Little Crooked (rr), Long (1) (rrr), 

 Long (3) (rr), Lower Turtle (rr), Mendota (sss), Meta (rrr), North Turtle 

 (rr), Owen (rrr), Paddock (rrr), Palmer (rrr), Pardee (rr), Pokegama (2) 

 (rr), Reserve (rr), Round (1) (rrr), Sand (1) (rrr), Sand (4) (rrr), Shell 

 (rrr), Sishebogema (rr), Tied Canoe (rr), Upper Turtle (rr), Wolf (r). 



One of the few species of the genus that is exclusively confined to 

 the plankton. The curving of the coenobe and the double series of 

 ovoid cells at once separates it from all other species. 



var. CAPITATUS G. M. Smith. PL 38, Figs. 15-16. 

 Trans. Wis. Acad. Sci., Arts, & Lett. ID 1 : 637, pi. 11, figs. 4-5. 1918. 



Cells with nodular thickenings at the poles. (Euplanktont). 

 Cells 5-11 /* broad, 11-23 p long. 8-celled colonies 22-27 /-i broad, 

 20-35 /* long. 



Center (rr). 



