RESULTS:

Summary: On the basis of a comparative study of 178 strains of cyanobacteria representative of this group of prokaryotes revised definitions of many genera are proposed. Revisions are designed to permit the generic identification of cultures often difficult through use of the field-based system of phycological classification. The differential characters proposed are both constant and readily determinable in cultured material. The 22 genera recognized are placed in five sections each distinguished by a particular pattern of structure and development. Generic descriptions are accompanied by strain histories brief accounts of strain properties and illustrations; one or more reference strains are proposed for each genus. The collection on which this analysis was based has been deposited in the American Type Culture Collection where strains will be listed under the generic designations proposed here.