Hypnea nigrescens Greville ex J. Agardh 1851

    Thallus green, purplish-green or purple, erect, several fronds arising from small discoid base, 10-16 cm high and 0.5-2 mm diameter. Thali sparsely branched, covered with ramuli from base to apex. Fertile branches thicker with densely crowded ramuli and attenuated. Cross section of thalli shows medulla composed of 3-4 layers of thick-walled, irregular cells, 80-180 µm in diameter surrounding small, often obscure axial cell. Cortex 1-2 cells thick; cells rounded to irregular, 6-20 µm in diameter.

    Tetrasporangial stichidia small lanceolate-rostate with a basal attenuate stipe; tetrasporangia zonate and borne terminally on corticating filaments; tetrasporangia measures 32-41 µm in long and 12-17 µm in broad.