Experiments were designed to test the ability of the aphotic speleoenvironment to support algal growth. The first series contained gelatin cultures of Scenedesmus placed in the cave at different localities in order to establish whether or not the microhabitats have any particular effect on the multiplication of the algae. No differences were found in the cultures after a three month incubation period in the cave, which could be traced to influences of microenvironmental conditions. Chlorella cultures in sterile Knop’s solution showed measurable growth in the cave whereas if the cultures were installed into sterilized cave water or were shielded by lead against possible radiation effects, no appreciable growth occurred. The presence or absence of magnetic field did not noticeably influence algal development. The experiments seemed to indicate that the algae tested are able to utilize soma kind of radiation in the complete darkness of the cava since, in the absence of organic material, appreciable amounts of molecular hydrogen or symbiotic activity, with iron bacteria, considerable growth occurred in a simple, strictly inorganic medium, whereas the cave waters seem to be deficient in some kind of inorganic salt required for algal nutrition. An investigation of algae living in the cave led to the determination of ten different taxa, the majority of which were Cyanophytes. Besides them, however, the cave may contain a more diversified algal population.