CYANOBACTERIA OF ROCKS AND SOILS OF THE ORINOCO LOWLANDS AND THE GUAYANA UPLANDS, VENEZUELA

The occurrence of 23 cyanobacterial species, belonging to 9 different genera and 5 cyanobacterial lichen species of 5 different genera on ex posed, open rock surfaces of inselbergs and on soil in savannas of the Orinoco lowlands and the Guayana uplands is described. Their distribu tion patterns and frequency within the different habitats are given. T he filamentous procaryotic blue-green algae/cyanobacteria Stigonema oc ellatum and Scytonema crassum, together with the unicellular cyanobact erium Gloeocapsa sanguinea were the most frequent species on rocks, wh ereas the filamentous cyanobacterium, Schizothriz telephoroides, domin ated in cyanobacterial mats on the savanna soil. All species showed in tensively coloured sheaths, either brown or yellow in the case of Stig onema ocellatum and Scytonema crassum, or red in Gloeocapsa sanguinea and Schizothrix telephoroides. In addition, a number of cyanobacterial lichens occurred.