A genus of filamentous cyanobacteria (section IV) in which the filaments when viewed under the microscope resemble strings of beads. Thick-walled, clear heterocysts can be seen at intervals along or at the ends of the filaments. Akinetes may be formed. Species are capable of fixing atmospheric nitrogen. They are common in aquatic environments, where they are usually planktonic, buoyed up by gas vacuoles. A. azollae lives in symbiotic association with the small floating fern, Azolla.
Subjects: Plant Sciences and Forestry.