Claviclonium ovatum (J.V.Lamour.) Kraft & Min-Thein

Scientific Description

Habit and structure. Thallus medium to dark red-brown, branches cartilaginous and ramuli soft, 10–20(–30) cm high, irregularly branched with long, terete, main branches 1–3 mm in diameter, bearing short, segmented (1–3 times) ramuli 5–10(–15) mm long and 1.5–2.5 mm in diameter, arising near the segmented branch apices and proliferously below. Holdfast discoid, 2–6 mm across, with a single frond; epilithic or on shells. Structure. Multiaxial, developing a broad, laxly filamentous, reticulate medulla of interconnected cells (many stellate), becoming dense with slender rhizoids in lower branches, and a pseudoparenchymatous cortex 2–3 cells thick, inner cells slightly larger than the ovoid outer cells (6–12 µm in diameter); outer cortex of main branches becoming meristematic, forming files of elongate cells. Rhodoplasts discoid, several per cell.

Reproduction.Sexual reproduction probably procarpic. Carpogonial branches 3-celled, borne on inner cortical cells sub-apically, inwardly directed with reflexed trichogynes. Supporting cell acting as auxiliary cell, producing several gonimoblast initials inwardly as adjacent vegetative cells produce a prominent pericarp around the disintegrating auxiliary cell. Gonimoblast filaments entering the pericarp and connecting to its cells, then forming centripetal branched tufts of filaments in the developing cavity, with single, terminal, ovoid to clavate carposporangia 10–18 µm in diameter. Cystocarps embedded, 0.7–1.2 mm across, with filamentous enveloping tissue and a cortical ostiole. Spermatangia unknown. Tetrasporangia scattered in the cortex, laterally pit-connected, ovoid, 28–40 µm long and 24–30 µm in diameter, zonately divided.

Distribution.Geraldton, W. Aust., to 16 km E of Eucla, S. Aust.

Habitat. C. ovatum is a moderately deep-water alga.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIA: 376 (1994)]