54 WISCONSIN PHYTOPLANKTON 



LYNGBYA BIRGEI G. M. Smith. PI. 7, Figs. 14-15. 



Bull. Torr. Bot. Cl. 43: 482, pi. 26, fiff. 28. 1916. 



Filaments free-floating, solitary, never forming floccose masses; 

 straight or slightly flexed. Sheaths firm, at times of considerable thick- 

 ness, hyaline, generally homogeneous, rarely lamellated, extending for 

 some distance beyond the trichome. Trichomes not attenuated at apices 

 and without constrictions at the cross walls. Terminal cells rounded 

 but not capitate at distal ends. Cell shape disciform. Cell contents 

 rarely homogeneous and with grey to olive green contents ; usually with 

 numerous pseudovacuoles. (Euplanktoiit). 



Cells 18-23 IL broad, 2-5.5 long. Sheaths .5-4 ^ thick. 



Balsam (rr), Bear Trap (cc), Big (cc), Deer (rrr), Elizabeth (ss), Fowler 

 (rrr), Half Moon (c), Kegonsa (aa), Lac la Belle (rr), Little Crooked (r), 

 Little Wood (rr), Loveless (rr), Lower Nashotab. (rr), Mary (ss), Mendota 

 (cc), Mercer (rr), Monona (cc), Mudhen (rr), Nagawicka (rr), Oconomowoc 

 (rr), Pope (rrr), Round (3) (sss), Sand (1) (r), .Spirit (sss), Squirrel (sss), 

 Upper Nashotah (cc), Upper Turtle (rr), Wapagossett (cc), Waubesa (cc), 

 Wolf (r). 



This is undoubtedly the alga that Trelease (Trans. Wis. Acad. Sci., 

 Arts, & Lett. 7: 124, pi. 10, fig. 6. 1888) reported from Lake Mendota 

 as Lyngbya Wollei Farlow. L. Wollei has been shown to be a Plecto- 

 nema (P. Wollei Farlow) and Trelease 's determination is undoubtedly 

 a mistake. 



TRICHODESMIUM Ehrenberg 1830. 



Trichomes laterally joined to form spindle- to scale-shaped, free- 

 floating colonies that are not enclosed by a gelatinous sheath. Trichomes 

 cylindrical, straight or spirally twisted, of the same thickness through- 

 out or with apices slightly attenuated. Apical cell undifferentiated, 

 or rounded and slightly capitate. Sheaths of trichomes very delicate. 

 Cells disciform to barrel-shaped. Cell contents homogeneous, granu- 

 lose, or with numerous pseudovacuoles. Heterocysts and resting spores 

 lacking. 



Reproduction by the formation of hormogones. 



TKICHODESMIUM LACUSTRE Klebahn. PI. 8, Fig. 1. 



Forschungsbr. a. d. Biol. Stat. zu Plon 3: 13. 1895; Flora 80: 271, pi. 4, flgy. 

 31-33. 1895. 



Trichomes laterally joined to form plate-like, free-floating masses 

 that are not enclosed by a gelatinous envelope. Filaments with a very 

 delicate, homogeneous sheath. Trichomes straight, not attenuated at 

 the apices, and with terminal cells rounded but not capitate. Cells 



