Microdictyon umbilicatum (Velley) Zanardini
Mem.Reale Ist.Veneto Sci. 10:461, Pl. 19 (1862)

Conservation Code: Not threatened
Naturalised Status: Native to Western Australia
Name Status: Current

Distribution

IMCRA Regions: Abrolhos Islands, Central West Coast, Leeuwin-Naturaliste, Ningaloo, St Vincent Gulf, Zuytdorp.

Local Government Areas (LGAs): Carnarvon, Cockburn, Coorow, Exmouth, Greater Geraldton, Northampton.

Scientific Description
John Huisman & Cheryl Parker, Thursday 8 September 2016

Habit and structure. Thallus medium to dark grey-green, 10–30(–45) cm across, firm but delicate, irregularly lobed and lacerate, with an obscure umbilicate base, probably usually epiphytic. Blade essentially monostromatic but with occasional tertiary branches displaced to one side of an earlier branch; branching of filaments alternate, opposite, or with up to six secondary filaments radiating from one point. Primary filaments 180–220 µm in diameter, cells L/B 1.5–3; secondary filaments 80–140 µm in diameter, L/B 2–4, with a rounded tip when free; attachment of filaments by smooth adherence of un-modified ultimate segments; meshes of net irregular; division of segments by ingrowth from the peripheral wall; chloroplast reticulate, composed of numerous, round, pyrenoid-bearing areas with narrow connections.

Reproduction. Unknown.

Distribution. Rottnest I., and Cape Riche, W. Aust., and from Coobowie, Yorke Pen, to Victor Harbor, and American River Inlet, Kangaroo I., S. Aust., Port Jackson, N.S.W. and Southport, Qld.

Habitat. Usually in calm bays and inlets.

[After Womersley, Mar. Benthic Fl. Southern Australia I: 217 (1984)]