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Soft-Bodied Stream Algae of California

Genus name:

Nostoc

Description:

Colonies microscopic or macroscopic, gelatinous, spherical or flat, often with a mucilaginous exterior. Filaments often curled inside the colony, loose or dense, concentrated near the surface. The sheath mucilaginous, firm, wide, and sometimes yellow to brownish, visible only in young colonies but confluent with common mucilage. Colonial mucilage colorless, yellowish green or brownish. Trichomes isopolar, moniliform. Cells barrel shaped or spherical, pale to bright blue-green or olive-green. Heterocysts barrel shaped or spherical, solitary, or two to three together, at ends of trichomes or intercalary. Akinetes ellipsoidal, slightly larger than vegetative cells, in rows between heterocysts. Reproduction by hormogonia, akinete germination or filament disintegration.