Is nostoc multicellular or unicellular?

Nostoc is a multicellular organism, but its cells are organized in a way that they form colonies or filamentous structures. The individual cells within the colony are arranged in a chain-like pattern. These colonies can aggregate into larger masses, which can be seen as the gelatinous mats commonly observed on moist soil, gravel, or other surfaces. While each cell is a single unit, the collective structure of these cells forms a multicellular arrangement.