In this section
Single heteropolar cyanobacterial filaments in a mucilaginous sheath. Base of filament begins at a heterocyte. False branching common, beginning at a heterocyte (which was originally intercalary before the emergence of the branch). Slight constrictions between cells are common; akinetes are rare. Organelles are absent from the cells, but granules are common. Forms fine tufts typically coloured blue or blue-green.