Order: Filamentous algae without branching; cell body mostly cylindrical.
Family: Chloroplasts plate-like or ribbon-like; sexual reproduction by isogamy.
Genus: Filaments without gelatinous sheath, consisting of up to 20 cells; without rhizoids; (Illustrations of the Japanese Freshwater Algae, 1977).
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P. lauterbornii ?
8.5 x 3 μm