Chondrophycus undulatus

Thallus rigid, cartilaginous, 4-7(-10) cm high, greenish-brown, dark purple to blackish, consisting of main erect axes, cylindrical below and compressed upward, to 4(-5.5) mm broad. Branching pinnate, or subdichotomous. Ultimate branchlets, short, knobby, with apical depressions on the top. In transverse section, cortex composed of 1-2 rows of slightly radially elongated cells, 12-24 μm across; medulla composed of roundish cells, 30-45 μm in diam. Lenticular thickenings in the medullary cell walls absent. Sporangia tetrahedral, scattered on the top of truncate or wart-like ultimate branchlets (converted into stichidia). Attachment by discoid holdfast to rocks.

Europe, Indian and Pacific Oceans.