Wrangelia decumbens Huisman

Scientific Description

Habit and structure. Thallus turf-like, decumbent, with short erect axes to 1–2 cm tall, these curving distally. Axes with (4–) 5 whorl branches per axial cell, one slightly longer branch arising at apices from convex surface, the remainder of medium length. Attachment rhizoids arising in clusters of 3 or 4 on basal cells of long whorl branches. Potentially indeterminate branches arising 1 per node from basal cells of whorl branches on concave surface. Whorl branches initially unilaterally branched, eventually appearing subdichotomously divided 5 or 6 times, the ultimate branches 2 or 3 cells long and terminating in a short mucronate cell. Nodal cortication by di- or trichotomously divided filaments arising from basal cells of 2 or 3 medium length whorl branches and encircling the primary axis. Basal cell of whorl branches 30–50 µm diam. when young, to 90 µm diam. when mature, relatively short [L:B c. 1]; median cells 40–60 µm diam. [L:B 7.5–10]; distal cells 10–15 µm diam. [L:B to 20]; terminal cell short and mucronate, 7–10 µm diam. [L:B c. 2].

Reproduction. Spermatangia borne near the base of whorl branches, terminal on cells, with an involucre of 3 or 4 simple filaments 2 or 3 cells long from the subtending cell. Other reproduction not observed.

Distribution. Known only from South Scott Reef, Western Australia.

Habitat. Epilithic.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 616–617 (2018)]