- Reference
- Ann.Mag.Nat.Hist. 334 (1855)
- Conservation Code
- Not threatened
- Naturalised Status
- Native to Western Australia
- Name Status
- Current
Scientific Description
Habit and structure. Thallus medium to dark red-brown, 5–20(–30) cm high, very mucilaginous, much branched irregularly with one to a few main axes and long lateral branches with conspicuous annulations due to the whorls of whorl-branchlets; branches terete, 1–2.5 mm in diameter below, tapering to 0.2–0.5 mm in diameter shortly below apices. Holdfast discoid, 1–5 mm across; epilithic. Structure. Apical cells 10–12 µm in diameter and L/D 0.5–1, increasing shortly below apices to 20–30 µm in diameter and L/D 1.2–1.5, and in lower thallus to 250–500 µm in diameter and L/D 1.2–1.5. Lateral branches originating from the basal cells of whorl-branchlets, becoming 16–20 cells long before initiating whorl-branchlets. Axial cells each with 4 whorl-branchlets of equal size, 350–750 µm long, forming annulations with the axial cells (or cortication) visible between them except near branch apices; whorl-branchlets branched 5–7 times di- or trichotomously, basal cells 35–75 µm in diameter and L/D 1–1.5, tapering to terminal cells 8–12 µm in diameter and L/D 1.2–2, often with terminal hairs; pyriform gland-cells occur on mid cells of the whorl-branchlets, often with crystal-like inclusions. Mature axes are corticated by rhizoids from the basal cells of whorl-branchlets, becoming dense below. Cells uninucleate; rhodoplasts elongate, ribbon like in older cells.
Reproduction. Gametophytes dioecious. Procarps single or opposite below the apices of short lateral branches which cease further growth; the supporting cell bears a curved 4-celled carpogonial branch, and post-fertilization a connecting cell is cut off and fuses with the auxiliary cell which forms a lower foot cell and an upper cell which develops successive rounded gonimolobes 90–140 µm across of ovoid carposporangia 20–25 µm in diameter; lower whorl-branchlets surround the carposporophyte. Spermatangia are cut off terminally on outer cells of the whorl-branchlets, ovoid or constricted, 3.5–5 µm in diameter. Tetrasporangia occur on third-order cells of the whorl-branchlets, sessile, subspherical, 60–120 µm in diameter.
Distribution.Hopetoun, W. Aust., to Phillip I., Vic., and N and E Tas.
Habitat. G. annulata is a deep-water species known mainly from the drift.
[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 65–67 (1998)]