Family: Filamentous algae without branching; cell body cylindrical; chloroplasts band-, plate- or star-shaped (Illustrations of The Japanese Fresh-water Algae, 1977).
Genus: Filament without branching; cell body cylindrical; one or several chloroplasts band-shaped, spirally arranged within the cell, pyrenoids present; septum with or without folded structure (Guide book to the "Photomicrographs of the Freshwater Algae", 1998). About 300 species (Illustrations of The Japanese Fresh-water Algae, 1977).
Spirogyra sp.
or Mougeotia ?
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Hiroshima, 1998