Spyridia squalida J.Agardh

Scientific Description

Habit and structure. Thallus grey-red to red-brown, when dried often appearing somewhat farinaceous, usually 10–30 cm high, robust, erect, irregularly and proliferously branched, with one to several axes, usually with long, much branched, laterals on all sides. All branches terete and corticated to their apices, axes and main branches linear, lesser branches basally constricted and bearing densely arranged ramelli, especially on their upper parts, sometimes denuded below. Holdfast small, discoid; epilithic. Structure. Axes 1.5–2.5 mm in diameter, denuded below or with short, proliferous branches, tapering slightly to branches 1–1.5 mm in diameter and lesser branches 0.5–1 mm in diameter. Segments largely obscured by cortication, L/D 0.3–0.5, with 16 periaxial cells and about twice as many internodal cells; cortication commencing within a few axial cells of apices, pseudoparenchymatous, 2–3 cells thick on lesser branches, several cells thick on axes. Ramelli one per segment close to apices, originating from periaxial cells and also scattered, adventitious, densely covering the lesser branches, sometimes persisting onto larger branches; ramelli 0.5–1(–1.5) mm and (10–)14–20(–24) cells long, larger cells (20–)30–40(–45) µm in diameter and L/D (1–)1.5–2 (–2.5). Ramelli with a single row of small nodal cells derived from 5–6 periaxial cells each of which cuts off 2–3 outer cells in the same transverse plane. Cells uninucleate; rhodoplasts discoid, becoming elongate in larger inner cells.

Reproduction. Gametophytes dioecious. Female axes developing as short, adventitious branchlets which are fairly heavily corticated but less so than in vegetative branches. Alternate segments each bear a procarp, with the sterile segments bearing ramelli. Usually three periaxial cells occur in fertile segments, one (the supporting cell) producing a 4-celled carpogonial branch. Two, or probably often 3, auxiliary cells are formed, leading to a carposporophyte with two or three lobes, short stalked and 0.5–0.8 mm in diameter. The pericarp develops similarly to that in other species. Spermatangia cover the lower 2–6 cells (except basal cell) of ramelli, forming a male organ 50–80 µm in diameter. Tetrasporangia borne on the lower several cells of the ramelli, largely on the upper (adaxial) side, 1(–2) per cell, sessile, spherical to slightly ovoid, 40–60 µm in diameter, tetrahedrally to sub-cruciately divided.

Distribution. Geographe Bay, W. Aust., to Waratah Bay, Vic.

Habitat. Usually in deep water (2–24 m deep).

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 377–379 (1998)]