Incendia homosorora K.R.Dixon

Scientific Description

Habit and structure. Thallus bright orange-red to deep red, with raised concentric bands, moderately calcified and flexible, forming expansive encrusting blades often with broad lobes free of the substratum at the margins. Hypothallus composed of sparingly branched, regularly parallel filaments of rectilinear cells 17–42 μm long and 5–12 μm tall, giving rise to assurgent perithallial filaments above and rhizoids below from their distal ends. Lower perithallus with elongate perithallial coxal cells and lower perithallial cells. Perithallial coxal cells bearing primarily obliquely orientated cellular projections that form secondary pit connections with adjacent cells to form oblique pseudofilaments. Lower cells of the perithallus forming irregularly orientated projections and secondary pit connections. Upper perithallus of beaded to rectilinear cells 15–28 μm long and 3–10 μm diam. below, decreasing in length distally and becoming ±isodiametric and rounded at the dorsal surface. Hairs embedded within the upper perithallus bullet-shaped, 17–25 μm long and 10–15 μm diam. Rhizoids long, 5–10 μm diam., multicellular, the basal cell short, embedded within the ventral cuticle.

Reproduction. Mature tetrasporangia to 85 μm long and 25 μm diam., borne laterally on the basal cells of otherwise long slender simple paraphyses in raised subcircular nemathecia to 2.5 mm diam. and 160 μm thick. Gametangia not observed.

Distribution. Known only from Adele Island and Browse Island in the Kimberley region of north-western Australia.

Habitat. Known from subtidal rock.

[After K.R. Dixon in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 215 (2018)]