Generic name: NODULARIA (Mertens in Jürgens) ex Bornet et Flahault 1888, nom. cons. Ann. Sci. Nat. Bot., ser. 7, 7: 243.
Synonyms: SPERMOSIRA Kützing, 1843. Phycol. gener., p. 213.[ NODULARIA Mertens,in Jurgens, Algae aquaticae, Dec. XV, n. 4, 1822, absque descriptione; - Agardh, Systema Algar., p. XXV, n. 40, 1824; - Sprengel, Systema vegetab., IV, pars 1a, p. 313, n.3424 ex Bornet et Flahault, 1886: Anabaena, Lyngbya, Oscillatoria, Spermosira, Sphaerozyga sp.]
Bornet et Flahault (1888): Fila libera vaginata. Trichomata sterilia eximie
aequalia. Vagina hyalina arcta, plerumque tenerrima, mucosa, nonnun- quam evanescens. Articuli breves depressi, disciformes. Heterocystae compressae. Sporae globosae, subglobosae
vel disciformes, in intervallo heterocystarum seriatae, episporio laevi. (Voyez Bornet et Thuret, Notes algologiques, pl. XXIX.).
Type species: Nodularia spumigena Mertens ex Bornet et Flahault 1888. 
Komárek (1992): Filamentous; filaments solitary or in groups or clusters, rarely in mats, isopolar, unbranched (without false or true branching), more or less straight, curved, coiled or irregularly spirally coiled with fine, diffluent sheaths of a special two-layered structure (type species), opened at both ends. Trichomes uniserial, cylindrical, rarely shortly and slightly attenuated at the ends of developed trichomes, constricted at cross walls, metameric, with more heterocytes in more or less
regular distances from one another. Cells shortly barrel-shaped, their length never exceeds the width, with (planktic species) or without (benthic species) gas vesicles joined in the aerotopes (two mentioned groups of species differ cytologically and ecologically - subgenera ?); gas vesicles occur facultatively only in planktic species. Cell content yellowish, pale olive-green or blue-green, thylakoids irregularly coiled, spread allover the cell volume, sometimes more gathered in the peripheral layer of cells. Heterocytes of the same shape of cells, sometimes slightly differ in their size (slightly smaller or larger than vegetative cells). Akinetes shortly barrel-shaped (shorter than wide), or spherical, developing apoheterocytic, but often with irregularities.
Genotype differences, molecular data:
Reproduction strategies, life cycles, cell division:
Komárek (1992): Cells divide crosswise to the trichome axis and grow into the original size before the next division, all cells capable to divide, without meristematic zones. Reproduction by hormogonia, disintegration of trichomes, and by akinetes.
Taxonomic position, higher hierarchy: Cyanophyceae,
Nostocales, Nostocaceae, Nostocoideae
Notes to taxonomy, misinterpretations:
Ecology, ecophysiology, ecological significance:
Komárek (1992): Four defined species (including the type species N. spumigena) are planktic with aerotopes within the cells forming sometimes heavy water blooms. They occur rarely in freshwater reservoirs, mainly in slightly salinic or brackish waters, salinic and coastal lakes (Baltic Sea; aestuaries of rivers - Spain, Australia; lakes in Western coast of North America, etc.). Three species are benthic, always without aerotopes, occurring in coastal or inland salinic and mineral pools, marshes and lakes (N. harveyana) , in alkalic streams and in littoral of lakes and pools (N. sphaerocarpa) or in rice fields as an important fixator of nitrogen (N. willei). N. harveyana has probably cosmopolitan distribution, N. sphaerocarpa is known mainly from the temperate zone (Europe), N. willei is probably pantropic. From other little known species, one is described from Antarctica, few taxa live surely in soils (probably special species), one species was described from thermal waters.
Physiology and biochemistry:
Distribution, endemism, problematic citations:
Reference strain:
Infrageneric scheme, species concept:

List of species:
Planktic types (with aerotopes):
Nodularia baltica Komárek, Hübel et M. Hübel 1993
Nodularia crassa (Voronichin) Komárek, Hübel et M. Hübel 1993
Nodularia litorea (Kützing) Thuret ex Komárek, Hübel et M. Hübel 1993
Nodularia spumigena Mertens ex Bornet et Flahault 1888. Ann. Sci. Nat. Bot., ser. VII, 7: 245 [morphologicaly and geographicaly different populations]

Benthic types:
Nodularia harveyana Thuret ex Bornet et Flahault 1888. Ann. Sci. Nat. Bot., ser. VII, 7: 243
Nodularia major (Kützing) ex Kirchner in Engler et Prantl 1900
Nodularia moravica Hindák, Šmarda et Komárek 2003
Nodularia quadrata Fritsch 1912
Nodularia rajkotii Gupte 1964
Nodularia sphaerocarpa Bornet et Flahault 1888. Ann. Sci. Nat. Bot., ser. VII, 7: 245
Nodularia turicensis
(Cramer) Hansgirg 1892
Nodularia willei Gardner 1927

Unclear taxa:
Nodularia aerophila Brabez 1941
Nodularia armorica Thuret ex Bornet et Flahault. 1888. Ann. Sci. Nat. Bot., ser. VII, 7: 245
Nodularia epiphytica
Gardner 1927
Nodularia hawaiiensis Tilden 1901
Nodularia mainensis Harvey 1899
Nodularia paludosa Wolle 1887 ex Stokes 1893
Nodularia skujae Gonzales-Guerrero 1928
Nodularia suhriana Kützing 1843
Nodularia tenuis G.S. West 1907

List of stains:
Komárek 1992
Application technology:
  2.1 taxonomy: Bornet & Flahault 1886-1888, Geitler 1932, Huber-Pestalozzi 1936, Bourrelly 1970, Nordin & Stein 1980, Šmarda et al. 1986, Komárek et al. 1992, Komárek 1992
  2.2 cytomorphology:
  2.3 16S rRNA sequencing:
  2.4 biology and life cycles:
  2.5 ecology: