Champia subcompressa Huisman

Scientific Description

Habit and structure. Thallus erect to decumbent, to 4 cm tall, red to purple-red, iridescent in situ, attached to the substratum by a discoid holdfast and secondary attachments, often with lateral fusions between branches. Branching mostly subopposite, occasionally verticillate. Axes terete to compressed, narrow near the thallus base and branch bases, broadening to 2.2 mm wide, segmented with slight constrictions 0.5–1.0 mm apart. Segments broader than long. Outer cellular layer composed of an inner layer of large hyaline cells, with smaller pigmented cells arising from their corners and forming complete or incomplete rosettes in surface view, these then producing darkly staining vesicular cells. Longitudinal filaments lining the inner surface and also scattered through the central cavity, 5–8 µm diam., with 1 or 2 complete cells and 2 partial cells per segment, laterally bearing spherical to pyriform vesicular cells 20–25 µm diam., generally 1 per filament cell. Diaphragms 1 cell thick.

Reproduction. Tetrasporangia arising in sori, often on abaxial surface, intercalary (best observed in surface view), attached antero-laterally to 2 cortical cells in an unmodified cortex, maturing mostly thallus inwardly, tetrahedrally divided, obovoid, 75–105 long, 60–90 µm diam. Other reproduction not observed.

Distribution. Montgomery Reef and Cassini Island, Western Australia.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 311–314 (2018); J.M. Huisman in Marine Plants of Australia: 139 (2019)]