Life-history studies on Rhodophyceae II. Halymenia floresia (Clem.) Ag.

Carpospores isolated from Halymenia floresia gametophytes collected at Banyuls (France, Pyrénées Orientales) grew into Acrochaetium-like plants. This Acrochaetium phase was capable of reproduction by monospores. Some of the Acrochaetium-like plants thus obtained differentiated into Halymenia sporophytes that produced monospores from monosporangial sori, and no tetrasporangia. These monospores developed into Acrochaetium-like or disciform plants, from some of which differentiated new Halymenia gametophytes. Carpospores isolated from Halymenia floresia gametophytes collected at Rovinj (Yugoslavia) grew into Acrochaetium-like plants. This Acrochaetium phase was capable of reproduction by monospores. Some of the Acrochaetium-like plants thus obtained differentiated into Halymenia plants that reproduced firstly by means of gemmae and secondly by the formation of “apical pompons” from necrotic apices. “Apical pompons” were Acrochaetiumlike plants grown from islands of living cortical cells lying amidst necrotic tissues. No new gametophytic Halymenia plants were obtained in cultures of Rovinj material, and therefore in culture the life-history was not completed. Vegetative isolates (from cortical filaments) of Rovinj gametophytes grew into Acrochaeliumlike plants reproducing by monosporulation. These Acrochaetium plants were not able to redifferentiate into Halymenia plants. Three types of such gametophytic Acrochaetium phases, differing in growth form and intensity of monosporulation, could be distinguished.