Inside the thin sheath are numerous unbranched hair-like structures called trichomes formed of short cells in a string.

When wet, Nostoc commune is bluish-green, olive green or brown but in dry conditions it becomes an inconspicuous, crisp brownish mat.

It is a terrestrial or freshwater species and forms loose clumps on soil, gravel and paved surfaces, among mosses and between cobbles.

[1] In Singapore, Nostoc commune is found growing on alkaline soils, in brackish water, in paddy fields, on cliffs and on wet rocks.

Nostoc commune contains photosynthetic pigments and the energy storing photosystems in membrane structures called thylakoids located in cytoplasm of the cells.