A TAXONOMIC STUDY OF THE GENUS LAURENCIA-(CERAMIALES, RHODOPHYTA) FROM VIETNAM - V - LAURENCIA CONCRETA CRIBB AND LAURENCIA-DINHII SP. NOV

The red alga Laurencia concreta Cribb (Rhodomelaceae, Ceramiales), rep orted for the first time from Vietnam, is characterised by the product ion of two vegetative periaxial cells from each axial segment. This, i n combination with other features, confirms its inclusion in the subge nus Chondrophycus. Laurencia dinhii Masuda et Kogame, sp. nov., endemi c to southern Vietnam, is characterised by the following set of morpho logical features: 1) a basal system composed of a single disc from whi ch a few terete to subterete axes arise; 2) the production of two vege tative periaxial cells from each axial segment; 3) the presence of a p alisade-like superficial cortical layer, 3) the absence of projecting superficial cortical cells; 5) the absence of longitudinally oriented secondary pit-connections between contiguous superficial cortical cell s; 6) the absence of lenticular thickenings in the walls of medullary cells; 7) the presence of intercellular spaces between contiguous medu llary cells; 8) a perpendicular arrangement of tetrasporangia, each of which is produced from the second periaxial cell in each fertile segm ent; 9) procarps produced from the last-formed (fourth) periaxial cell of the terminal segment of a two-celled female trichoblast; and 10) f lask-shaped cystocarps.