Collections of a preliminary type carried out in Crystal Cave, Kentucky, resulted in the identification of seven algal taxa. A Chamaesiphon (Dermocarpales) and an Asterocytis (Bangioidea) are reported for the first time from a speleo-environment. As no correlation could be found among the algae occurring in Crystal Cave and those of nearby Mammoth Cave the conclusion is reached that the cave algal floras do not originate from the algal vegetation of the surface but may have gotten into the caves at the time of the latter’s formation.