Cellular division in some colonial forms occurs in many different planes. This results in irregularly shaped colonies. Merismopedia Cellular division in some colonial forms of blue- green algae occurs in only two dimensions. In the genus Merismopedia , cellular division is in one plane. The resulting colonies are, therefore, one cell thick and rectangular in shape.
Growth occurs only along a single axis.
Filamentous species may be unbranched, have true branching, or have false branching. Some filamentous species have specialized cells within the chain of cells. Oscillatoria Oscillatoria is a genus of filamentous blue-green algae. Oscillatoria does not have a sheath surrounding the filament. Lyngbya Lyngbya is a genus of unbranched filamentous species of blue-green algae.