Plocamium angustum (J.Agardh) Hook.f. & Harv.
London J.Bot. 404 (1847)

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

Distribution

Beard’s Provinces: South-West Province.

IBRA Regions: Esperance Plains, Swan Coastal Plain.

IBRA Subregions: Perth, Recherche.

IMCRA Regions: Boags, Central West Coast, Leeuwin-Naturaliste, WA South Coast.

Local Government Areas (LGAs): Cockburn, Dandaragan, Esperance, Mandurah.

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

Habit and structure. Thallus to 25cm high, with numerous, erect, slender, rather linear axes arising from the basal stolons. Axes usually 0.5–1(–1.5) mm broad, bearing ramuli in alternating pairs, the upper often developing into a lateral branch similar to the axes; lower ramuli subulate, 1–1.5(–2) mm long, less than 0.5 mm broad at their base, usually entire but in some plants with several small serrations or spines on the abaxial margin.

Reproduction. Sexual thalli dioecious. Cystocarps sessile on adaxial base of ramulus or on adjacent axis, globular, smooth to slightly verrucose, 600–900 µm across. Spermatangia covering the surface of slender ramuli, becoming tufted and basally branched, the tufts enlarging with age and in some plants stichidia usually unbranched and swollen, 60–100µm in diameter, terete and fairly straight, the stalk remaining slender; tetrasporangia 50–70 µm long and 25–30 µm in diameter, zonately divided.

Distribution. New Zealand. Cannan Reefs, Great Australian Bight, S. Aust., to Tuggerah Lakes, N.S.W. and around Tas.

Habitat. Common on coasts of rough to moderate wave action and known from shaded pools near low water level to 50 m.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIA: 378–379 (1994)]