Giraudia robusta S.Skinner & Womersley
Phycologia 168, figs 11-21, 34, 35, 53-56 (1984)
Conservation Code:
Not threatened
Naturalised Status: Native to Western Australia
Name Status:
Current
Scientific Description
John Huisman & Cheryl Parker,
Monday 20 June 2011
Habit and structure. Thallus medium to dark brown, (1–)3–6(–8) mm high, pulvinate with free, stiff, erect axes, epiphytic on Posidonia and Amphibolis (rarely on fucoid algae). Basal plate monostromatic, of loose or compact radiating filaments on the host surface. Medullary filaments strongly developed, forming a stalk (0.5–)1–3 mm long to the upper polystichous axes; filaments subdichotomous, cells terete below, becoming pyriform to ovoid above, 10–20(–35) µm in diameter and L/B 1–6, with buttress rhizoids formed in the upper medulla, and the upper cells bearing the erect axes. Erect axes stiff, terete, 1–3 mm long, arising from a uniseriate or 2–3 cells broad base below the meristematic zone which persists only to maturity, (70–)100–200 µm broad centrally with tiers of 5–8(–9) cells, then tapering to the uniseriate apex (often several cells long) which usually continues as a single phaeophycean hair; uni- or biseriate laterals usually occur near apices of axes; cells of mature axes tending to become slightly six-sided in face view due to displacement in successive tiers, 15–30 µm across and L/B 1–2.5, with numerous discoid phaeoplasts each with a pyrenoid and prominent physodes. Phaeophycean hairs terminal and lateral from the upper axis cells, solitary, 15–28 µm in diameter.Microthallus myrionemoid 0.5–1 mm across, with short, erect, filaments 200–250 µm and 10–15 cells long, 12–15 µm in diameter, cells L/B 1.5–2, with long, narrow ascocysts, phaeophycean hairs and terete, multiseriate plurilocular sporangia.
Reproduction. Plurilocular sporangia of two kinds: (1) borne laterally from bases of erect axes, pedicellate, simple, terete to lanceolate, multiseriate, 250–500 µm long and 35–40 µm in diameter, and (2) borne laterally on upper laterals of erect axes, sessile or pedicellate, elongate ovoid to conical, 30–80 µm long and 15–20(–25) µm in diameter.Unilocular sporangia borne on upper medullary cells at base of erect axes, elongate ovoid to pyriform, 120–250 µm long and 40–50(–60) µm in diameter.
Distribution. From Rottnest I., W. Aust., to Robe, S. Aust. and the N coast of Tas.
[After Womersley, Mar. Benthic Fl. Southern Australia II: 308–310 (1987)]
