Halymenia dilatata Zanardini 1851

Division     Rhodophyta
Class     Florideophyceae
Order     Halymeniales
Family    Halymeniales
SynonymSebdenia dilatata (Zanardini) De Toni 1900

    Thallus erect, rose, dark red to reddish brown colour, and surface highly mucilaginous, 20-72 cm high. Thallus with small basal attaching disc, the single or occasionally two, rarely more stipitate erect fronds. Stipe very short, horny and sub-terete expanding abruptly into the broad lamina; Lamina as long as broad, variable in shape, ranging from flabelliform to oblong, entire or palmatifid, the lobes often imbricate; lamina margin with numerous small denticulate proliferations and frilled in appearance. Lamina surface usually maculate, the patches irregular and soriform; occasionally a few large proliferations, similar to the main blade, also present. Thallus 100 – 200 µm thick; Medulla large, composed of transverse medullary filaments, 6 – 10 µm broad, intermingled with the stellate cells and rhizoids; Stellate cells 25 – 36 µm diameter with arms up to 150 µm long. Rhizoidal cells 2 – 4 µm width and thick walled; Cortex narrow, few layered, the inner cells larger and gradually decreasing towards the margin, irregular to sub-stellate, 15-23 x 30-45 µm. Peripheral layer cells spherical, 5-9 µm diameter. Tetrasporangia cruciate, scattered over the surface of the thallus, ovoid to subspherical, 25-30 µm diameter.



Distribution in India

Appa Island, Anaipar island, Keelakarai, Manapad, Mulli Island, Tuticorin, Pamban, Pudumadam Salli Island and Koswari Island (Desikachary et al., 1990; Ganesan et al., 2023)