Herposiphonia falcata (Kutzing) De Toni 1903

    Thalli dark brown to pinkish red in colour and more delicate. Thalli attached to the substratum by unicellular haptera with or without digitate base. Apex of the prostrate filaments curved upwards. Prostrate indeterminate axes terete with segments about as long as broad with 10-12 pericentral cells. Determinate branches cylindrical curved towards apex look like sickle shaped and apices moderately blunt. Basal segment consists of 5-6 pericentrals and 10 -12 pericentrals at rest of the determinate branches. Determinate branches measures 700-1000µm long, 50-100µm in diameter, comprising 17-23 (28) segments, segments shorter than breadth (0.4-0.8 times as long as broad).

    Spermatangial clusters, subcylindrical and 3-5 borne on the adaxial side of the each determinate branch measure 70-128 µm long and 25-37 µm broad. Spermatangial cluster with single stalk cell and sterile cell (5-8 µm long and 8-11µm broad); spermatium 2-5 µm in diameter. Cystocarps urn-shaped and measure 460-600 µm long and 400-490 µm broad, one per branchlet, carpospores clavate shape measures 35-60 µm long and 10-20 µm broad. Tetrasporangia in series of 4-8 in determinate branches measure 80-95µm in diameter and tetrahedrally arranged tetraspores.