Hypnea charoides J.V.Lamour.

Scientific Description

Habit and structure.Thallus light to medium red to red-brown, (5–)10–20 cm high, tufted and much branched irregularly, with an entangled base and erect branches, usually not strongly percurrent; branches terete throughout, covered (usually densely) with slender spinous branchlets 1–3 mm long and 100–250 µm in diameter, mostly directed at right angles to the parent branch. Attachment by small, discoid, haptera; epiphytic, usually on Amphibolis, occasionally on other algae. Structure uniaxial, apical cell conspicuous, axial filament recognisable throughout, 20–50(–90) µm in diameter with cells L/D 4–8, surrounded by a medulla 2–3 cells broad, cells ovoid and (30–)50–90(–150) µm in diameter with few secondary pit-connections, and a small-celled cortex 1–2 cells broad, outer cells ovoid and 10–20 µm in diameter, with odd smaller, often darker staining, cells 4–9 µm across cut off outwardly and lying over the margins of their initials. Rhodoplasts discoid, numerous per cell.

Reproduction. Sexual thalli dioecious. Carpogonial branches and early post-fertilization stages not observed. Carposporophyte with a lax reticulum of elongate cells developed from several basal cells and with the upper cells in pit-connection with inner pericarp cells, producing clusters of smaller cells laterally with each cell producing single (occasionally a chain of two) subspherical to ovoid carposporangia 25–35 µm in diameter. Cystocarps sessile on lateral branchlets, globular and 0.5–1.5 mm in diameter, base broad to slightly constricted, with a pericarp 3–5 cells thick, cells ovoid and separated, non-ostiolate. Spermatangia in sori near base of branchlets, cut off from outer cortical cells via initials, in short, often branched chains, ovoid, 2–3 µm in diameter. Tetrasporangia in nemathecia near the base of the branchlets, basally to laterally pit-connected to inner cortical cells, ovoid, 50–80 µm long and 20–35 µm in diameter, zonately divided by successive but rapid divisions.

Distribution.Port Denison, W. Aust., to Cape Jaffa, S. Aust., and N Tas.

Habitat. H. charoides is found under moderate wave action and commonly epiphytic on Amphibolis.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIA: 441–444 (1994)]