Rhode Island. Quidnessett. (Bennett). New York. In some abun- 

 dance near Schenectady. (Holden). Pennsylvania. In stagnant water. 

 (Wolle). Ohio. Sandusky Bay. (Riddle). Indiana. Edge of Monon 

 Pond, Bloomington. (Brown). Minnesota. Home Brook, Gull Lake Bi- 

 ological Station, Cass County. July 1893. (Tilden); In lake two miles west 

 of Inver Grove, St. Paul. April 1908. (Misz). Nebraska. Found occa- 

 sionally in stagnant water about Lincoln. (Saunders). 



174. Arthrospira gomontiana Setchell. Notes on some Gyanophyceae 01 

 New England. Bull. Torr. Bot. Club. 22: 430. 1895. De Toni. Syll. 

 Algar. 5: 208. 1907. 



Collins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 5. no. ISS. 1896. 

 Collins. Phycological Notes of the late Isaac Holden. — II. Rhodora. 7: 

 235. 1905. 



Plant mass floating, verdigris-green; trichomes 2.5-3 mic. in diameter, 

 regularly twisted into a rather loose spiral about 6 mic. in diameter, the 

 distance between the turns being 16-18 mic; apical cell not at all capitate; 

 cells 4-5 mic. in length; transverse walls indistinct, with few granules; cell 

 contents usually showing large vacuoles, light blue-green. 



Connecticut. Floating in verdigris-green patches, on the pool below 

 F"actory Pond, Bridgeport. July 1895. (Setchell and Holden). 



Genus SPIRULINA Turpin. 

 Diet, d'hist. nat. de Levrault. 50: 309. 1827. 



Trichomes unicellular, cylindrical, without a sheath, forming a regu- 

 lar, more or less loose or close spiral; apex of trichome not tapering; cell 

 contents homogeneous or slightly granular. 



I Turns of the spiral not close together. 



1 Trichomes 1.2-1.8 mic. in diameter, forming a more or less loose, 



somewhat irregular spiral 3,2-5 mic. in diameter, the distance be- 

 tween the turns being 3-5 mic. S. meneghiniana 



2 Trichomes 1.2-1.7 mic. in diameter, forming a somewhat loose, regu- 



lar spiral 2.5-4 ™ic. in diameter, the distance between the turns 

 being 2.7-5 mic. S. major 



3 Trichomes 2 mic. in diameter, forming an especially regular spiral 5 



mic. in diameter, the distance between the turns being 5 mic. 



S. nordstedtii 



4 Trichomes .6-.9 mic. in diameter, forming an especially regular spiral 



1.5-2.5 mic. in diameter, the distance between the turns being 1.2-2 

 mic. S. subtilissima 



5 Trichomes .4 mic. in diameter, forming an especially regular spiral 



1.4-1.6 mic. in diameter, the distance between the turns being i mic. 



S. tenerrima 



6 Trichomes .9 mic. in diameter, forming a very loose spiral 1.5 mic. 



in diameter, the distance between the turns being 3.2 mic. 



S. caldaria 



