^'' ' . agile, very much constricted at 



joints; apex of trichome straight or curved, neither tapering nor capitate; 

 apical cell rotund; calyptra none; cells of unequal length, 2.3-16 mic. long; 

 transverse walls pellucid, not granulated; protoplasm containing a few 

 large, refringent granules. 



Minnesota. In arm of Mississippi River (old channel), St. Paul Park. 

 October 1897. (Freeman). Montana. In hot water. Lo Lo Hot Springs, 

 Lo Lo. September 1898. (Griffiths). Wyoming. Covering bottom of 



creek in swift current. Temperature 47.5° C. Near Upper Geyser Basin, 

 Yellowstone National Park. July 1896. (Tilden). Washington. On mud 

 by the roadside. La Conner, Skagit County. (Gardner). 



147- Oscillatoria minnesotensis Tilden. American Algae. Cent. VI. no. 

 S96. 1902. 



Plate IV. fig. 21. 



Plant mass thin, dark blue-green; trichomes 2-5 mic. in diameter, more 

 or less curved, especially constricted at joints; apex of trichome straight 

 or slightly bent, neither tapering nor capitate; apical cell rotund; calyptra 

 none; cells 2-4 mic. in length; transverse walls pellucid; cell contents 

 homogeneous. 



Minnesota. On sides of stone quarry under dripping water. Near 

 Campus, University of Minnesota, Minneapolis, February 1902. (Lilley). 



The plant differs from O. g e m i n a t a in the length of the cells, 

 in the absence of granules, and in its habitat. Like that species, also it 

 resembles a Phormidium, but the trichomes when examined were oscil- 

 lating rapidly thus showing conclusively that it was an Oscillatoria. 



148. Oscillatoria chlorina Kuetzing. Phyc. Gen. 185. 1853. Gomont. Monogr. 

 Oscill. 243. 1893. De Toni. Syll. Algar. 5: 172. 1907. 

 Wood. Contr. Hist. Fresh-Water Algae North America. 18. pi. i. f. i. 

 1872. WoUe. Fresh-Water Algae U. S. 311. pi. 206. f. 6. 1887. Collins. 

 Algae of Middlesex County, Massachusetts. 15. 1888. Bessey, Poimd and 

 Clements. Additions to the Reported Flora of the State. Bot. Surv. Ne- 

 braska, s: 13. 1901. Collins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 

 19. no. 901. 1902. Setchell and Gardner. Algae of Northwestern America. 

 Univ. Calif. Pub. Bot. i: 183. 1903. Clark. The Holophytic Plankton of 

 Lakes, Atitlan and Amatitlan, Guatemala. Proc. Biol. Soc. Wash. 21: 97. 

 1908. 



Plate IV. fig. 22. 



Plant mass very thin, cobwebby, yellowish green; trichomes 3.5-4 mic. 

 in diameter, straight or curved, fragile, not constricted at joints; apex of 

 trichome straight or curved, not tapering; apical cell rotund; calyptra 

 none; cells 3.7-8 mic. in length; transverse walls pellucid, not granulated; 

 cell contents nearly homogeneous, orange or yellowish green. 



Greenland. (Richter). Massachusetts. Newton. (Farlow). Penn- 

 sylvania. In stagnant brick pond. Near Philadelphia. (Wood). Nebraska. 

 In culture in greenhouse. Lincoln. (Bessey). Washington. Growing on 

 decaying vegetation in a small pool, submerged about two feet. Whidbey 



