Myxophyceae 6t 



G Trichomes ^.5-4 mic. in diameter, constricted at joints; apex of 

 trichome very gradually*tapering, hooked or undulating; cells 

 quadrate or longer than the diameter O. numidica 

 H Trichomes 5.5-8 mic. in diameter, slightly constricted at joints; 

 apex of trichome very gradually tapering, hooked or undulat- 

 ing; cells quadrate or longer than the diameter, very long near 

 the apex O. cortiana 



1 Trichomes 5.5-9 mic. in diameter, constricted at joints; apex of 

 trichome very gradually tapering, undulating and finally hooked; 

 apical cell obtuse; cells shorter than their diameter 



O. okeni 

 J Trichomes 8-13 mic. in diameter, scarcely constricted at joints, 

 sometimes twisted in loose spirals; apex of trichome briefly or 

 gradually tapering and hooked; apical cell obtuse; cells shorter 

 than their diameter O. chalybea 



K Trichomes 8-10 mic. in diameter, straight, somewhat constricted 

 at joints; apex of trichome often slightly tapering, obtuse, 

 straight or curved O. subsalsa 



L Trichomes 15.5-18.5 mic. in diameter, straight; apex of trichome 

 usually curved, somewhat tapering, obtuse-truncate 



O. percursa 



VI Plants living in fresh water, sometimes in hot water; trichomes regu- 

 larly terebriform in apical portion or forming a spiral throughout their en- 

 tire length, more or less tapering in the apical portion. 



1 Trichomes 6-8 mic. in diameter, forming a lax and regular spiral 



through their entire length, or straight and hooked at the apex; 

 apical cell pointed, not capitate O. boryana 



2 Trichomes 4-6.5 mic. in diameter, flexuous, straigfht below, loosely 



spiralled and terebriform above; apical cell obtuse, not capitate 



O. terebriformis 



Species not well understood. 



O. subtorulosa 



126. Oscillatoria prolifica (Greville) Gomont. Monographie des Oscil- 

 lariees. 225. pi. 6. f. 8. 1893. De Toni. Syll. Algar. 5: 149. 1907. 



Farlow, Anderson and Eaton. Algae Am.-Bor. exsicc. no. 229. 1889. 

 (O. diffusa Farlow). Trelease. The "Working" of the Madison Lakes. 

 Trans. Wis. Acad. Sci. Arts and Letters. 7: 122. pi. 10. 1889. Hauck and 

 Richter. Phykotheka Universalis, no. 477. 1892. Collins, Holden and Setch- 

 ell. Phyc. Bor.-Am. Fasc. 4. no. 154. 1896. Moore. The Pollution of Water 

 Supplies by Algae. Rhodora. i : 100. 1899; The causes of the red-brown color 

 in certain Cyanophyceae. Soc. Plant. Morph. and Phys. Sci. N. S. 13: 

 248. 1901. Hyams and Richards. Notes on Oscillatoria prolifica (Gre- 

 ville). Tech. Quart. 14: 302. 1901; 15: 3o8. 1902; 17: 270. 1904. Olive. 

 Notes on the occurrence of Oscillatoria prolifica (Greville) Gomont in the 

 Ice of Pine Lake, Waukesha County, Wisconsin. Trans. Wis. Acad. Sci. 

 15: 124. 1905. 



