Caulocystis uvifera (C.Agardh) Aresch.

Scientific Description

Habit and structure. Thallus medium to dark brown, (10–)20–40(–60) cm long, with a short stipe and main axis bearing 1–4 mature primary branches, each much branched with laterals of limited growth. Holdfast discoid, (3–)5–10 mm across; epilithic. Primary branches terete, 2–3 (–4) mm in diameter, bearing irregularly radial and usually densely arranged laterals, 1–5 mm apart, giving the branch an elongate-conical shape, with occasional secondary branches from the lower branch axis, and scattered vesicles borne directly on the primary branch axes (rarely on secondary branch axes); branch axes becoming denuded basally, with short, stubby residues; vesicles on a pedicel 2–5 mm long, subspherical to ovoid, 3–7(–9) mm in diameter, mutic or occasionally with a short mucro 1–2 mm long. Lateral ramuli (1–)2–many times furcate or laterally branched at intervals of 1–5 cm, terete, (2–)3–9 cm long and 0.5–1.5 mm in diameter, usually simple when young or on secondary branches, with prominent cryptostomata. Growth from a single, three-sided, apical cell in an apical depression. Structure of a central compact medulla of elongate cells with few hyphae, and a cortex of large, isodiametric, cells decreasing to the surface meristoderm.

Reproduction. Thallus monoecious. Receptacles developed from upper ends of ramuli, simple, terete to lanciform, smooth, (0.5–)1–2(–3) cm long and 1–2 mm in diameter, with scattered ostioles. Conceptacles numerous, bisexual, basal columella with some phaeophycean hairs and paraphyses; oogonia basal, sessile, ovoid, 80–160 µm long and 50–90 µm in diameter; antheridia sessile or on branched paraphyses, elongate-ovoid, 20–30 µm long and 7–10 µm in diameter.

Distribution.From Shark Bay, W. Aust., around southern Australia and Tas., to Coogee, N.S.W. Norfolk I.

Habitat. C. uvifera occurs from low tide level to deep water, usually under slight to moderate water movement.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 359 (1987)]