Gloiosiphonia capillaris has been cultured through two successive life cycles. Sterile gametophytes, which were described previously (Edelstein, 1970), became fertile and formed spermatangial sori and cystocarps on the same thallus. Carpospores gave rise to crustose tetrasporophytes. Numerous crops of tetraspores, which were produced over a prolonged period, gave rise again to fertile gametophytes. In some instances the basal, prostrate system of the gametophyte persisted in culture for over 18 months without forming erect thalli. Additional means of vegetative reproduction were found to occur in this species.