Hypnea spinella

Thallus wiry, erect or forming densely intricate mats or cushions, 1-3 cm high, light brown to dark red. Branching dense, multifarious. Branches cylindrical, 0.2-0.4 mm diam., tapering towards the apices, often anastomosing with other branches by dense rhizoidal tufts issuing from branch and branchlets tips. Branches densely covered with short lateral branchlets. Branchlets numerous, needle-like, spine or spur-like, to 0.1-2.5(-4) mm long, tapering to apices. Apices acute. Tetrasporangial sori swollen encircling middle or distal part of ultimate branchlets, 160-200(-230) μm diam., 300(-600) μm long. Tetrasporangia subcylindrical, zonately divided, 15-17 μm in diam., 25-30 μm long, develop in the sori. Cystocarps spherical, 500-800 μm diam., sessile, develop laterally on axes. Attachment by discoid holdfast and creeping branches with secondary holdfasts. Growing in the low intertidal to upper subtidal zones on dead corals, rocks or epiphytic on larger algae.

Tropical and subtropical waters of Atlantic, Indian and Pacific Oceans.