AN ACCOUNT OF THE RED ALGAL GENUS SPOROLITHON (SPOROLITHACEAE, CORALLINALES) IN SOUTHERN AUSTRALIA

Sporolithon (Sporolithaceae, Corallinales) is represented in southern Australia by S. durum (Foslie) Townsend et Woelkerling, comb. nov. The species and the development of male and female-carposporangial concep tacles and tetrasporangial compartments and sori are described in deta il for the first time. Information on etymology, collections examined, distribution, seasonality and habit and comparisons with other specie s is also included. Published records of S. erythraeum from southern A ustralia have not been substantiated. Two further species have been re ported under the generic name Archaeolithothamnion. Archaeolithothamni on australasicum is a species of uncertain status, while A. mirabile i s conspecific with Lithothamnion muelleri Lenormand ex Rosanoff. Diffe rences between the Sporolithaceae and the Corallinaceae, and the delim itation of genera within the Sporolithaceae, are reconsidered in relat ion to new data on S. durum. The Sporolithaceae is characterised by te trasporangia that produce cruciately arranged spores and develop withi n calcified sporangial compartments, while the Corallinaceae is charac terised by tetrasporangia that produce zonately arranged spores that d o not develop in calcified sporangial compartments. Two genera of Spor olithaceae are recognised: Heydrichia, in which tetrasporangial compar tments are enclosed by modified filaments to form sporangial complexes ; and Sporolithon, in which tetrasporangial compartments are not enclo sed by modified filaments and sporangial complexes are absent. The con cepts of conceptacle and sorus also are reconsidered.