States (Massachusetts and New Jersey to South Dakota). I have 

 collected the species in southern Louisiana and in Panama. 

 Attached to the sandy bottom of lakes in shallow water. Wis. 



NODULARIA Mertens, in Jiirgens 1822, Dec. 15, No. 4 

 A sheathed filament, either sohtary among other algae or forming 

 thin expansions or tufts, aquatic or subaerial, on moist soil; cells 

 disc-shaped or compressed spheroidal, constricted at the cross walls; 

 heterocysts similarly compressed, about % of the width in length; 

 gonidia spherical or disc-shaped, occurring in short (sometimes 

 long ) series, intercalary. 



Key to the Species 



Filaments 4-6m in diameter; gonidia 6-8^ in diameter N. Harveyana 



Filaments 8-12-(18)At in diameter; gonidia 12^ in diameter N. spumigena 



Nodularia Harveyana (Thw.) Thuret 1875, p. 378 

 Filaments usually solitary; nearly straight, sometimes flexuous but 

 not entangled or coiled. Sheaths colorless and thin, usually close 

 but sometimes diffluent and becoming indistinct. Cells 4-6/i, in 

 diameter, 1/3 the diameter in length or, before division, nearly as 

 long as broad. Apical cell obtusely conical. Gonidia nearly spherical 

 or compressed-spheroidal; about 8/* in diameter; yellowish-brown 

 in color. 



Tychoplankter; in shallow water. Wis. 



Nodularia spumigena Mertens in Jiirgens 1822, Dec. 15, No. 4 



PI. 122, Figs. 3-5 



Filaments usually entangled and clustered in a loose, gelatinous 

 mass; sometimes sohtary; 8-12/* in diameter. Cells disc-shaped, very 

 much compressed; constricted at the cross walls; 6-7.8-(10)/i, in 

 diameter, 5.6/* long. Gonidia intercalary but not necessarily near 

 the heterocysts; 12/* in diameter, 8-9/i long. 



Uncommon; found among algae in lakes of especially hard water; 

 also adhering to the culms of rushes submerged in shallow water. 

 Wis. 



APHANIZOMENON Morren 1838, p. 11 

 Filamentous; united to form fusiform or plate-hke bundles and 

 flakes of parallel trichomes, which are free-floating. Trichomes 

 relatively short, tapering very slightly at both ends. Cells quadrate- 



[527] 



