ABSTRACT
A classifi cation provides a platform to identify a particular organism to the level of species. The art of classifi cation is known as taxonomy and phylogeny helps to draw evolutionary relationships between the organisms classifi ed. So a phylogenetic system of classifi cation serves a better purpose for classifi cation as well as inferring evolutionary relationships. The earliest taxonomic treatises considered cyanobacteria as an algal group under the general name blue-green algae (Thuret, 1875; Bornet and Flahault, 1888; Gomont, 1892). Traditionally thus, the blue-green algae have been classifi ed along with eukaryotic algae under the International Code of Botanical Nomenclature (ICBN). As per rules of ICBN, a type species has to be deposited in a recognized Herbarium either in a dried state or fi xed algal material. Due to the limitation in the availability of pure culture strains and the paucity of information on their biochemical and genetic features, the earlier workers depended mostly on morphological characteristics. Due to the absence of membrane-bound cell
organelles, the blue-green algae were considered closer to bacteria (Cohn, 1872, 1875). Subsequent to the publication of taxonomic keys on heterocystous forms (Bornet and Flahault, 1888) and the Oscillatoriaceae (Gomont, 1892), a comprehensive account on the taxonomy of these organisms has been presented by Geitler (1932) wherein 145 genera encompassing 1300 species have been classifi ed into 20 Families under three Orders. The “Geitlerian” approach provided new impetus for a number of taxonomists to classify them (Fritsch, 1945; Drouet and Daily, 1956; Golubic, 1967; Bourelly, 1970 and many others) from time to time.
