Pterocladiella tenuis

Thallus erect, cartilaginous, gregarious, bushy, 5–20 cm high, dark purple-red to dark grayish-green, consisting of creeping and erect axes. Branching distichous, pinnate, to 4 orders, in pyramidal outline. Erect axes subcylindrical below, flattened above, 1.5–2.5 mm width, 220–300 μm thick. Branches of all orders flattened, tapering to the base. Branches of the first order almost of the same width with the main axis. Branches and branchlets arranged opposite or alternate. In transverse section, cortical cells 8–11×6 μm; medullary cells rounded, 28–42 μm width; cells of rhizoidal filaments are located in outer medulla. Tetrasporangia cruciately divided, 45–50×20–35 μm, in ultimate spatulate branchlets; cystocarps – below apices on one side. Attachment by peglike rhizoidal holdfasts. Growing on rocks, dead corals in the middle intertidal to the upper subtidal in sites exposed to strong wave action.

China, Japan, Taiwan, Korea, Russia.