A MORPHOLOGICAL-STUDY OF LAURENCIA-PALISADA (RHODOMELACEAE, RHODOPHYTA)

The red alga Laurencia palisada Yamada (Rhodomelaceae, Ceramiales), th e lectotype species of the section Palisadae, is characterised by the following set of features: 1) rigidly cartilaginous upright axes arisi ng from a discoid holdfast; 2) a shift of branching from a distichous to a spiral manner distally; 3) the production of two periaxial cells per vegetative axial segment; 4) the absence of longitudinally oriente d secondary pit-connections between cintiguous superficial cortical ce lls; 5) the absence of projecting superficial cortical cells; 6) the p resence of a palisade-like cortical layer; 7) the absence of lenticula r thickenings in the walls of medullary cells; 8) the absence of corps en cerise in any cell; 9) the production of two tetrasporangium-beari ng periaxial cells from each fertile segment; 10) a perpendicular arra ngement of tetrasporangia; 11) procarps produced from the last-formed (fourth) peraxial cell of the terminal segment of a two-celled female trichoblast; 12) flask-shaped cystocarps; and 13) distally positioned spermatangial nuclei.