Polysiphonia abscissoides Womersley

Scientific Description

Habit and structure. Thallus dark red-brown, 4–12 cm high, densely tufted with numerous, much branched, slender, erect branches arising from prostrate filaments. Attachment by rhizoids from prostrate filaments; epilithic. Structure. Prostrate filaments (100–)150–300 µm in diameter with segments L/D 1–1.5(–2), with unicellular rhizoids cut off from pericentral cells; erect branches 100–175(–200) µm in diameter with segments L/D 1.5–2 ,extending to 3–6(–10) in mid parts, tapering gradually to 70–100 µm with segments L/D 1–1.5 in upper parts and (40–)50–60 µm with segments L/D 0.5–1 near apices; apices straight to slightly curved, with fairly prominent apical cells and a few to numerous trichoblasts; lateral branches irregular and sparse but often 2–4 segments apart near apices, of limited growth and without trichoblasts; branches arising in place of trichoblasts; cicatrigenous branches absent (?). Pericentral cells 5 (occasionally 4), elongate except near apices, ecorticate throughout; trichoblasts (or scar cells) occasional in lower (older) parts, more plentiful near apices, simple or once furcate, basal cells 12–18 µm in diameter, sometimes plentiful and 2–3 times furcate in fertile plants. Rhodoplasts discoid, irregularly placed.

Reproduction. Gametophytes dioecious. Carposporophytes with a slight basal fusion cell and short gonimoblast bearing clavate terminal carposporangia 20–35 µm in diameter. Cystocarps short-stalked, ovoid, becoming urceolate, 250–350(–450) µm in diameter; pericarp ostiolate, 2 cells thick, outer cells isodiametric, angular. Spermatangial branches developing as one branch of a trichoblast, cylindrical and gently tapering, (150–)200–350 µm long and 50–75 µm in diameter, without a sterile apical cell when mature. Tetrasporangia forming regular, straight to gently spiral series in upper branches, often descending below 2–3 branchings, only slightly distorting the segments, subspherical, 50–75 µm in diameter.

Distribution.Shark Bay, W. Aust?., and SE Tas. South I., New Zealand.

Habitat. P. abscissoides appears to be essentially a low intertidal species.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 199–200 (2003)]