Stictosporum nitophylloides (Harv.) J.Agardh

Scientific Description

Habit and structure. Thallus erect, medium to dark red or red-brown, firm and drying cartilaginous, 8–15 cm high, complanately and subdichotomously branched at intervals of 1–4 cm, with occasional proliferations near the base, branches (3–)5–10(–15) mm broad, 180–300 µm thick, axils rounded, margins throughout with evenly spaced spinous ramuli 0.5–1 mm long, branch apices broad and rounded. Holdfast discoid, 1–3 mm across; epilithic. Structure uniaxial, with a small apical cell in an apical notch, with each axial cell producing two periaxial cells, the alternating lateral ones producing filaments and the short transverse ones contributing to the cortex; axial filament soon indistinguishable. Medulla weakly developed, with a few elongate cells and rhizoids, cortex usually two cells thick with large, polyhedral outer cells, without rosettes but with groups of small cells bearing hairs. Rhodoplasts discoid, numerous per cell.

Reproduction. Sexual thalli probably dioecious; procarpic. Carpogonial branches 3-celled, borne laterally on an inner supporting cell which bears several branched, small-celled filaments, with the basal cell of one filament serving as the auxiliary cell; gonimoblast initial produced outwardly. Carposporophyte with basal auxiliary and other cells with radiating gonimoblast filaments with branched chains of ovoid to angular carposporangia 25–55 µm in diameter, with the pericarp formed of branched anticlinal rows of small cells on both sides. Cystocarps swelling the thallus on both sides, 0.8–1.2 mm across, ostiolate on one side. Spermatangia unknown. Tetrasporangia scattered in the cortex, transformed from inner cortical cells and pit-connected basally, ovoid, 75–110 µm in diameter, zonately divided.

Distribution.Garden I., W. Aust., to D' Estrees Bay, Kangaroo I., S. Aust.

Habitat. S. nitophylloides is a distinctive, deep-water alga.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIA: 431 (1994)]