Culture studies on the rare brown alga Phaeostroma longisetum comb.nov. and its common relative P. pustulosum from Greenland

Culture studies have shown that the rarely reported alga, Symphyocarpus longisetus , agrees with the type species of Phaeostroma with regard to its mode of formation of plurilocular sporangia, number of chloroplasts, and type of true hairs, and disagrees with the type species of Symphyocarpus. The new combination, Phaeostroma longisetum , is proposed. Unilocular sporangia are reported for the first time in this species. The life history is of the direct type under all conditions tested. The species grows and reproduces also at 15°C LD conditions although generally considered an arctic species.
Phaeostroma pustulosum probably also has a homophasic, direct type of life history. The plants are either pseudoparenchymatous discs or branched filaments. The filamentous thalli are in agreement with the younger taxon Phaeostroma aequale (= Streblonema aequale).