Nostoc

nostoc

Any of the cyanobacteria that make up the genus Nostoc. The cells are arranged in beadlike chains grouped together in a gelatinous mass. Ranging from microscopic to walnut-sized, nostoc masses may be found on soil and floating in still water. A special thick-walled cell has the ability to withstand drying for long periods of time. After 70 years of dry storage, cells of one species can germinate into filaments when moistened. Like most other cyanobacteria, nostocs contain two pigments and are capable of nitrogen fixation.

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Nostoc 

a genus of blue-green algae of the class Hor-mogonaceae. There are approximately 50 species, living in almost all climatic zones, in fresh waters and on damp cliffs and soil. Colonies of the algae are gelatinous and spherical, with a diameter of up to 10 cm. They resemble tapes or filaments and are free-living or sedentary. The colonies consist of single rows of filaments buried in the slime. Each filament is composed of thick-walled cells called heterocysts. The algae reproduce by spores or vegetatively, with bits of the filaments breaking off. There are some nitrogen-fixing species. Some species of Nostoc are used as food in Asian countries.