- Reference
- Schmitz & Falkenberg, Nat.Pflanzenfam. [Engler & Prantl] I(2):461 (1897)
- Conservation Code
- Not threatened
- Naturalised Status
- Native to Western Australia
- Name Status
- Current
Scientific Description
Habit and structure. Thallus dark brown-red, 2–4 cm high, forming dense mats usually on low-intertidal rock, with prostate indeterminate filaments bearing erect, simple or branched, ecorticate, determinate filaments. Attachment of indeterminate filaments by unicellular rhizoids. Structure. Apices of indeterminate filaments curved upwards, dorsiventral, apical cell 25–30 µm in diameter, axes cutting off 10–18 pericentral cells and becoming 130–180 µm in diameter with segments L/D 0.5–1. Erect laterals with conical apical cells 16–28 µm in diameter (including thick walls), producing trichoblasts several segments apart and more-or-less in 2 rows, with 12–22 pericentral cells 12–16 µm broad, surrounding axial cells 40–50 µm broad and L/D 0.8–1.2; filaments (100–)120–200 µm in diameter, segments L/D (0.3–)0.5–0.8(–1). Branching endogenous, frequent from indeterminate filaments, usually sparse from erect filaments. Trichoblasts 0.5–1 mm long, branched from 3–4 basal cells 30–40 µm in diameter and L/D 1–2(–3), upper cells long. Rhizoids with digitate haptera, cut off from pericentral cells. Cells multinucleate; rhodoplasts discoid to elongate, chained in larger cells.
Reproduction. Gametophytes dioecious, unknown in Australian collections. Procarps on the third segment of trichoblasts, developing 5–7 pericentral cells with one (the supporting cell) cutting off a basal and 2 lateral sterile cells and a 4-celled carpogonial branch. Carposporophyte with a basal fusion cell and a branched gonimoblast with clavate terminal carposporangia. Cystocarps ovoid, sessile; pericarp ostiolate, probably ecorticate. Spermatangial organs on lower cells of trichoblasts, reported as 60–300 µm broad. Tetrasporangia in upper branches, in 2 longitudinal rows of opposite pairs over 6–10 segments, 30–65 µm in diameter, with 2 cover cells similar to pericentral cells.
Distribution.In southern Australia, from King George Sound, W. Aust., to Port Elliot, S. Aust. Western Europe, California, South Africa, Seychelles.
Habitat. O. simpliciusculus appears to be a rare alga on southern Australian coasts, confined to lower eulittoral rock.
[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 335–337 (2003)]