Abstract
A. heterocladum Funk from the Aegean Sea was isolated and studied in culture and a life history of the Polysiphonia-type was demonstrated. Cytological investigation indicates a chromosome number of n = 46 .+-. 4 in the gametophytes and 2n = 86 .+-. 8 in the tetrasporophytes. The taxonomical position of the species and its relationship to other Antithamnieae is discussed.