gg WISCONSIN PHYTOPLA.NKTON 



KEY TO THE SPECIES. 



Poles of cells without spines O. PABVULTIM 



Poles of cells with spines - CAPITATUM 



OpmocYTroM PARVULUM (Perty) A. Braun. PI. 15, Fig. 11. 

 Alg. unicell. 55. 1855; Lemmermann, Hedwigia 38: 33, pi. 4, figs. 30-33. 1899. 



Cells cylindrical, several times as long as broad ; straight, arcuate, or 

 spiral; poles rounded and without spines. Chromatophores several, 

 H-shaped in cross section, pale yellowish-green. Oil droplets rarely 

 present. ( Ty choplanktont ) . 



Cells 3-9 /i broad. 



Fishtrap (rrr). 



OPHIOCYTIUM CAPITATUM Wolle. PI. 15, Figs. 12-13. 

 Freshw. Algae of U. S. 176, pi. 158, figs. 3-7. 1887. 



Cells solitary ; arcuate, sigmoid, or spiral cylinders with poles rounded 

 and the same size as or slightly larger than the median portion of the 

 cell. Length of cell 5-10 times the breadth. Poles of cells with a 

 single short, straight, or slightly curved spine. ( Ty choplanktont) . 



Cells 5-10 /x broad, up to 85 p. long. Spines 5-7 /* long. 



Tied Canoe (rrr). 



var. LONGISPINUM (Mobius) Lemmermann. PI. 15, Figs. 14-16. 

 Hedwigia 38: 32, pi. 4, figs. 21-25. 1899. 



Cells cylindrical ; straight, arcuate, or spirally twisted, with a single 

 long spine at each pole that is nearly as long as the cell. (Euplank- 

 tont). 



Diam. cells 4.5-6 //,. Length of spines 16-50 p.. 



George (rr), Loon (rr). 



Order HETEROTRICHALES. 



Cells in simple, unbranched filaments; with or without a gelatinous 

 envelope. Cell wall firm, fairly thick, lamellated in structure and 

 breaking down into H-shaped pieces at the time of reproduction. Chro- 

 matophores few to several, yellowish-green, disciform, and parietal. 

 Cells usually uninucleate. Assimilation product oil, not starch. 



Asexual reproduction by the formation of aplanospores or by zoo- 

 spores with two cilia of unequal length. 



