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Hapalospongidion capitatum Womersley

Reference
Mar.Benth.Fl.S.Australia 75, fig. 20 (1987)
Conservation Code
Not threatened
Naturalised Status
Native to Western Australia
Name Status
Current

Scientific Description

Habit and structure. Thallus dark brown, crustose but gelatinous when fresh, a few mm across to confluent patches a cm or so across, mostly 500–750 µm thick, firmly adherent to the rock substrate, without rhizoids. Basal layer of radiating filaments of rectangular cells 5–8 µm across, becoming 2–3 cells thick, with each cell producing two erect, simple (rarely branched) filaments transversely to the basal cell rows. Erect filaments at first slightly assurgent, soon becoming separated, of 40–60 cells; most filaments with lower cells 4–6 µm in diameter and L/B 2–3, mid cells 3–4 µm in diameter and L/B 4–6, surmounted by 3–7 cells of increasing diameter to the subspherical to ovoid terminal cell 10–12 µm in diameter; occasional erect filaments distinctly broader (8–10 µm) throughout with the cylindrical terminal cell of similar diameter; hairs not seen. Growth of erect filaments by intercalary divisions of subapical and lower cells. Cells with one to a few laminate phaeoplasts and numerous scattered physodes.

Reproduction. By plurilocular sporangia originating below (often just below) the apex of erect filaments but becoming terminal by loss of upper part of filament, occasionally on short lateral branches from below another sporangium, becoming 40–60(–80) µm long and 15–20 µm in diameter with loculi 2–4 µm across; occasional sporangia develop as, or with, lateral protrusions and all sporangia are situated within the thallus.

Distribution. Only known from the type collection, Frenchman’s Bay, King George Sound, W. Aust.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 75–76 (1987)]