Freshwater epiphytic cyanoprokaryotes from central Mexico III. The Genus StichosiphonGeitler 1932

This is the third study on the cyanoprokaryotic (cyanophycean, cyanobacterial) epiphytes, colonizing submersed substrates (mainly other filamentous algae) in streaming waters in central Mexico. The species of the genus StichosiphonGeitler 1932 were all made synonyms of S. sansibaricus by Drouet & Daily (1956). We have found six morphotypes, which can be distinguished at the species level, five corresponding to species defined by previous authors and one new species, S. exiguus. The morphological variation of the Mexican populations was studied, and the comparison with the original descriptions of type specimens is presented. The characters applied in the taxonomy of the genus Stichosiphon are discussed. One other species, known from Burma (Skuja 1949), was redefined according to the present diacritical features for this genus (S. skujae).