52 WISCONSIN PHYTOPLANKTON 



OSCILLATORIA TENUIS C. A. Agardh. PI. 7, Fig. 6. 



Algarum decades 2: 25. 1813; Gomont, Ann. Sci. Nat. 7 S6r. Bot. 16: 220, 

 pi. 7, figs. 2-3. 1892. 



Filaments solitary or in floccose masses that are pale blue-green in 

 color. Trichomes straight, slightly constricted at the cross walls. Termi- 

 nal cells the same diameter as those in the median portion of the trich- 

 ome, straight or curved; apical cells rounded but not capitate. Cell 

 shape disciform. Cell contents homogeneous except for a row of gran- 

 ules along the cross walls. (Tychoplanktont). 



Cells 4-10 fi broad, 2.6-5 M long. 



Monona (rr). 



var. TERGESTINA (Kiitzing) Rabenhorst. PI. 7, Figs. 7-8. 



Flora Eur. Algarum 2: 102. 1865. 



Trichomes narrower than the foregoing. (Tychoplanktont). 

 Cells 46 /A broad. 

 Geneva (ss). 



LYNGBYA C. A. Agardh. 1824. 



Filaments solitary or interwoven to form floccose masses; free-float- 

 ing or in an expanded stratum. Sheaths of filaments narrow, firm, 

 hyaline or colored, homogeneous or lamellated, generally projecting 

 for some distance beyond the trichome. Filaments unbranched, cylin- 

 drical ; straight, flexed, or twisted into regular spirals. Trichomes gen- 

 erally the same thickness throughout, rarely slightly attenuated at the 

 apices ; sometimes constricted at the cross walls. Apical cell with distal 

 end rounded or slightly capitate. Cell contents homogeneous, granu- 

 lose, or with numerous pseudovacuoles ; grey, pale to bright blue-green 

 or variously colored. 



Reproduction by the formation of hormogones. 



KEY TO THE SPECIES. 



Filaments not over 4 n in thickness, with pale blue-green to grey cell contents. 



Filaments straight L. LIMNOTICA 



Filaments in regularly coiled spirals L. COXTOBTA 



Filaments over 10 M in diameter, contents deeply colored L. BIRGEI 



LYNGBYA LJMNETICA Lemmermann. PI. 7, Figs. 9-11. 



Bot. Cent. 76: 154. 1898; Kryptogamenfl. d. Mark Brandenburg 3, Algen 1: 

 135, 102, fig. 8. 1907. 



Filaments free-floating, generally solitary ; straight or slightly flexed. 

 Trichomes not constricted at the cross walls. Apical cells the same 



