Polysiphonia morrowii

Thallus coarse filamentous, bushy, semiprostrate, bearing erect axes to 22 cm high, almost black in color. Axis percurrent of four pericentral cells, uncorticated. Branching alternate with narrow angles. Branches of the first and second orders naked or with sickleshaped incurved, simple or branched branchlets clinging to each other and forming tangled clumps. Branches of the third order densely covered with spirally arranged short spinose branchlets with straight or recurved apices. Cystocarps narrowly oval, develop on spinose branchlets. Sporangia spherical, 60-120 μm diam., develop in spinose and in axial adventitious branchlets. Attachment by rhizoids issuing from prostrate axes. Growing on intertidal and subtidal rocky.

Europe, North America, Japan, China, Korea, Russia (the Sea of Japan, Okhotsk and Bering Seas).