AN ACCOUNT OF AUSTROLITHON INTUMESCENS GEN ET SP-NOV AND BOREOLITHON VAN-HEURCKII (HEYDRICH) GEN ET COMB-NOV (AUSTROLITHOIDEAE SUBFAM NOV, CORALLINACEAE, RHODOPHYTA)

The Austrolithoideae (subfam. nov.), comprising Austrolithon (gen. nov .) and Boreolithon (gen. nov.), differs from other subfamilies in the Corallinaceae (Corallinales, Rhodophyta) in possessing multiporate tet rasporangial conceptacles and in lacking cell fusions, secondary pit c onnections and genicula. Austrolithon and Boreolithon both include sin gle known species: A. intumescens (sp. nov.) from southern Australia a nd B. van-heurckii (comb. nov.) from the British Isles and France. Aus trolithon and Boreolithon differ in growth form (unconsolidated vs. en crusting), habit (almost entirely endophytic vs. epigenous) and thallu s construction (partly diffuse and partly pseudoparenchymatous and mon omerous vs, largely pseudoparenchymatous and dimerous). Type material of both species was examined. A detailed morphological and anatomical account of Austrolithon intumescens is provided and new data are prese nted for Boreolithon van-heurckii. Information on etymology, collectio ns examined, and distribution, seasonality and habitat is also include d for both species, and Austrolithon intumescens is compared with othe r endophytic Corallinaceae. Eight subfamilies of Corallinaceae are now recognized, based on phenetic comparisons; similarities and differenc es are considered briefly.