Euptilota articulata (J.Agardh) F.Schmitz

Scientific Description

Habit and structure. Thallus erect, medium to dark red, 5–25 cm high, pinnate, complanately and densely branched for 4 or 5 orders, laterals alternate, becoming densely corticated except close to apices, axes and laterals slightly compressed, 0.5–2 mm broad. Ultimate largely ecorticate branchlets alternately distichous, 200–500 µm long, pinnules 70–100 µm long. Holdfast densely rhizoidal, 2–10 mm across; epilithic. Structure. Apical filaments alternately branched, with oblique alternating cross walls, apical cells 20–25 µm in diameter and L/D 0.6–1, axial cells enlarging to 400–600 µm in diameter in lower thallus; cortication commencing usually within 10–15 cells of apices, originating from basal cells of laterals, soon becoming dense and largely obscuring the axial cells, outer cells small, isodiametric to irregular and angular, 10–15 µm across; older axes with a multilayered cortex around 3–4 large central cells, with rhizoidal filaments of long cells between the axial cells and inner, larger, cortical cells. Cells uninucleate; rhodoplasts discoid.

Reproduction. Gametophytes dioecious. Carpogonial branches borne on a supporting cell on subapical cells of ecorticate laterals, opposite a branch with often 2 or 3 in close succession, probably with 1 or 2 other sterile periaxial cells; post-fertilization stages unknown. Carposporophytes situated at the apex of short lateral branches, with a single gonimolobe 300–500 µm across of ovoid carposporangia 30–70 µm in diameter, surrounded by an involucre of simple, tapering, branchlets 300–450 µm and 8–12 cells long, mid cells 35–50 µm in diameter and L/D 0.7–1.2. Spermatangia in dense clusters on terminal and lower cells of pinnules. Tetrasporangia borne laterally or terminally on the pinnules, sessile, subspherical to slightly ovoid, 70–100 µm in diameter, tetrahedrally divided.

Distribution. From Flat Rocks (S of Geraldton) and Houtman Abrolhos, W. Aust., to Coffs Harbour and Lord Howe I., N.S.W., and E Tas.

Habitat. E. articulata is a common species on rough-water coasts throughout southern and south-western Australia, from shaded relatively shallow situations to deep water.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 355–356 (1998)]