Snow algae of the Windmill Islands, continental Antarctica. Mesotaenium berggrenii (Zygnematales, Chlorophyta) the alga of grey snow

A saccoderm desmid Mesotaenium berggrenii forma (Mesotaeniaceae) occurring as a major component of the snow algal flora is reported from the Windmill Islands region of Continental Antarctica. Stages of the life cycle of the species are illustrated. The local distribution of the species is outlined, habitat conditions described, taxonomy, reproduction and survival strategies discussed. Morphological and nuclear size classes indicate the possibility of polyploidy in the species.