50 WISCONSIN PHYTOPLANKTON 



KEY TO THE SPECIES. 



Turns of spirals not over 5 M in diameter S. MAJOB 



Turns of spirals over 10 n in diameter S. PBIITCEPS 



SPIRULINA MAJOR Kiitzing. PI. 7, Fig. 1. 



Phycol. generalis 183. 1843; Gomont, Ann. Sci. Nat. 7 Ser., Dot. 16: 251, pi. 7, 

 fig. 29. 1892. 



Filaments free-floating and solitary, or forming a greenish, scum. 

 Trichomes in a more or less loose spiral that is straight or bent. Cell 

 contents homogeneous ; bright blue-green. Sheath of filament lacking. 

 ( Tychoplanktont) . 



Triehomes 1.2-1.7 /x in diameter. Spirals 2.5-4 /* broad, 2.7-5 

 fj. between turns. 



White Ash (rrr). 



SPIRULINA PRINCEPS (W. & G. S. West) G. S. West emend. PI. 7, Fig. 2. 



Jour. Linn. Soc. Bot. 38: 179, pi. 9, fig. 5. 1907; W. & G. S. West, Trans. Linn. 

 Soc. Bot. 2 -Ser., Bot. 6: 205. 1902. 



Trichomes solitary, in loose spirals that may be straight or curved. 

 Ends of trichomes blunt or rounded. Cell contents homogeneous or 

 with a few scattered granules; bright blue-green. (Tychoplanktont). 



Trichomes 3-5 /* broad. Spirals 8.8-16 ^ broad, 9.5-12 p between 



turns. 



Poor Farm (rrr). 



OSCILLATORIA Vaueher 1803. 



Trichomes possessing a peculiar power of spontaneous movement of 

 an oscillating, rolling, or gliding type; free-floating; solitary or in 

 flocculent masses ; sometimes forming strata in moist places. Trichomes 

 unbranched, cylindrical, entirely without or with barely perceptible 

 sheaths. Ends of trichomes straight, slightly attenuated, but never at- 

 tenuated to a point. Terminal cells rounded or calyptrate. Cell shape 

 cylindrical to disciform. Cell contents usually homogeneous or granu- 

 lose, rarely with pseudovacuoles. Color of cells variable. 



Reproduction by hormogones. 



