A new red alga Herposiphonia japonica (Rhodomelaceae, Ceramiales) from the north-western Pacific

The red alga Herposiphonia japonica Masuda et Shimada, sp. nov. (Rhodomelaceae, Ceramiales) is described from the Pacific coast of central Japan. It is characterized by the following combination of features: 1) a relatively broad (150-200 μm) prostrate axis bearing either a determinate branch or an indeterminate branch (or branch primordium) from every segment, commonly in a sequence of three determinate branches followed by one indeterminate branch; 2) determinate branches that are terete and relatively long (to 2.5 mm long and consisting of 15-32 segments) and slender (75-80 μm in diameter); 3) central axial cells in mature segments of determinate branches that are caskshaped and 30-50 μm in diameter (2-3 times broader than surrounding pericentral cells); 4) proximal positions of tetrasporangia, procarpial trichoblasts, and spermatangial branches on fertile determinate branches; 5) a secund arrangement of 4-12 spermatangial branches in two rows along the concave or convex side (or the lateral and either the concave or convex side) of fertile branches and sometimes in three rows along the lateral and either the concave or convex side or along these three sides; and 6) a slight thickening of the proximal segments of cystocarp-bearing branches.