Peyssonnelia webervanbosseae K.R.Dixon

Scientific Description

Habit and structure. Thallus dark to very dark maroon, lacking radial striae and concentric bands, heavily calcified both within the thallus and hypobasally. Blades forming extensive closely appressed crusts that follow the contours of the substratum giving the thallus surface a smooth but lumpy texture, 150–275 µm and 7–16 cells thick, predominantly hypothallial, with a dorsal perithallus of assurgent filaments arising from a monostromatic hypothallus of horizontally spreading parallel filaments. Blades can become mesothallic over uneven substrata, the hypothallus additionally developing a ventral perithallial layer of descending filaments. Dorsal perithallus composed of 2 layers: a lower layer of larger often rounded and elongate cells traversed by irregularly orientated horizontal filaments, and an upper layer of deeply pigmented often tiered squat cells. Upper perithallial layer initially thin, but becoming much thicker in older parts of the thallus. Hairs absent. Rhizoids unicellular, to 200 µm long and 5–12 µm diam.

Reproduction. Reproduction not seen.

Distribution. Endemic to Adele Island, north-western Australia.

[After K.R. Dixon in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 231 (2018)]