SEMNOCARPA GEN-NOV (RHODOPHYTA, RHODYMENIALES) FROM SOUTHERN AND WESTERN-AUSTRALIA

An examination of cystocarps from the rarely collected southern Austra lian alga currently known as Lomentaria corynephora (J. Agardh) Kylin has shown it to be a member of the Rhodymeniales but incorrectly place d in Lomentaria. As it is not referable to any of the genera presently ascribed to the order, the new genus Semnocarpa is proposed to accomm odate its suite of unique features. Semnocarpa closely resembles Lomen taria in habit and in having basally septate branches, a peripheral ne twork of widely separated medullary filaments around the cell-free (bu t mucilage-filled) centres of the main and lateral axes, gland cells d irected inwardly on scattered medullary cells, and tetrasporangia prod uced laterally from surface cortical cells that line deep cavities in the branch surfaces. Features of the mature cystocarp, however, strong ly differentiate Semnocarpa from Lomentaria. The carposporophyte has a fusion cell in which outlines of the component cells remain discernib le, as opposed to having a fully consolidated fusion cell, and is laxl y enclosed in a system of filaments derived from surrounding inner cor tical cells. The cystocarp is entirely submerged within the bearing br anch, there being no protuberant pericarp derived from the outer corte x of the sort previously thought to be a uniform feature of the family Lomentariaceae and virtually all Rhodymeniales. These features sugges t that Semnocarpa is likely to be a highly derived member of the Lomen tariaceae. A second species is newly described from material collected in Western Australia. Semnocarpa minuta sp. nov. differs from S. cory nephora in its exclusively epiphytic habit, two-layered medulla, small er stature and extensive crustose holdfast.