Reticulocaulis mucosissimus I.A.Abbott

Scientific Description

Habit and structure. Thallus erect, to 10 mm tall, hirsute, with a percurrent primary axis bearing lateral branches at irregular intervals, resulting in a somewhat pyramidal outline. Primary axes terete, to 1.2 mm diam., tapering to a pointed apex. Lateral branches 0.5–0.7 mm diam. at base of branch, similar in form to primary axes. Primary axial cells elongate, 7–10 μm diam. [L:B 10–12], each bearing 2 periaxial cells, the first at the distal end of the cell, the second at about midcell. Both periaxial cells producing cortical fascicles, these sparingly dichotomously divided, with lower cylindrical cells 4–8 μm diam. [L:B 8–10], and upper spherical to obovoid cells 10–12 μm diam. The first periaxial cell of the cortical fascicle becoming elongate, the second cell remaining subspherical, both producing basipetal rhizoidal filaments that form secondary pit connections with each other and enlarge considerably to form a subpseudoparenchymatous layer around the axial filament, the entire structure (axial cells and enlarged cells) reaching a diameter of c. 250 μm. Enlarged cells initiating secondary cortical cells that can form a branched cortical fascicle or remain simple.

Reproduction. Spermatangia in clusters on outer cortical cells; clusters subspherical, 12–17 μm diam., with individual spermatangia c. 2.5 μm diam. Other reproductive structures not observed.

Distribution. Known from the Hawaiian Islands, Oman, the Canary Islands, Brazil, and north-western Australia.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 151 (2018)]