Neosiphonia japonica

Thallus erect, coarse filamentous, bushy, solitary or in tufts, 3-5(-12) cm high, dark reddish-brown. Branching dichotomous below to irregularly alternate or unilateral above. Erect axes and branches to 1 mm in diam., polysiphonous, composed of 4 pericentral cells, corticated below or sometimes corticated throughout the thallus except ultimate branchlets. Branches of the first order long, widely angled. Branches of the following orders narrowly angled. Ulimate branchlets short, 120-190 μm diam., tapering near the tips. Trichoblasts deciduous, occurring alternately from each segment in spiral sequence with one-fourth divergence. Sporangia spherical, 80-115 μm diam., tetrahedrally divided, develop in the middle portion of ultimate branchlets. Cystocarps scattered on ultimate branchlets, broadly oval, near to spherical, 350-500×460-580 μm. Attachment by a disc-like holdfast or by rhizoids from prostrate axes. Growing on hard substrate or epiphytic.

Russia (Bering and Okhotsk Seas, the Sea of Japan). Japan (Honshu Island), China (the Yellow Sea).