Dioicous. In dark green, as wet somewhat shiny carpets in spray from streams and waterfalls, seldom on dry stream banks. The main axis usually 1 1/2-2 cm long and 0.6-0.7 mm wide. Both ventral and dorsal surface slightly convex, the edges are rounded and show no indications of wings, marginal cells slightly smaller than the inner ones. The median portion is usually 5-6 cells thick, all cells thin-walled. The cells of the surface layer are usually 20-40 x 30-50 x 12-20 µ, the marginal cells 20-24 x 12-14 µ, the interior ones about 60 x 90 x 120 µ. At intervals of about 1 mm on each side the axis gives off obliquely (about 45°) spreading branches, either short with limited growth or 2-3 mm long, sometimes giving rise to a new axis, sometimes also narrow, stolon-like branches. The long primary branches give rise to subopposite secondary branches 1-1 1/2 mm long. The primary and secondary branches have a convex dorsal and plane-convex ventral surface, the margins often deflexed. The median portion is 4-5 cells thick, the structure is essentially like that of the axis except that the margins are slightly crenulated. Surface cells 12-20 x 30 µ, interior cells to 70 x 100 µ. The apices have a shallow incision at the growing point. Single slime-papillae are seen on the ventral surface of the thallus. Oil bodies absent. Male branches from the side of the axis and primary branches, spoon-shaped, with margin crenulate by often claw-like cells. Antheridia 4-5, separated by walls one cell thick and the openings of the chambers separated by two cells. Female organs on short branches, bud-like, with short wings and short cilia, ending with ellipsoid, sometimes claw-like cells. Calyptra smooth. Sporogone opens with 4 valves, wails with regular long cells and regular semiannular thickenings. Spores 12-14 µ, smooth, brown. Elaters about 140 µ long and 8-10 µbroad, monospirate, orange-browm, spiral to 6 µ broad.
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