Cheilosporum sagittatum (J.V.Lamour.) Aresch.
Species genera et ordines algarum 545 (1852)
Conservation Code:
Not threatened
Naturalised Status: Native to Western Australia
Name Status:
Current
Scientific Description
John Huisman & Cheryl Parker,
Monday 20 June 2011
Habit and structure. Thallus medium red-brown, fading to grey-red, 4–10 cm high, in dense tufts of numerous erect fronds, axes and main branches dichotomously and largely complanately branched, each intergeniculum with two opposite, strongly developed, compressed, acute lobes with upper margins (400–)600–1300 µm long, lower margin passing to the base or to two-thirds up the intergeniculum, intergenicula 500–1250 µm long and 250–400 µm broad below the lobes. Holdfasts crustose, soon developing terete to slightly compressed, unlobed stolons 250–400 µm in diameter in an entangled mass 0.5–12 mm across; epilithic. Structure. Branch apices with a thin mucilaginous cover and without epithallial cells. Intergenicula with 5–10(–12) arched tiers of medullary cells, extending to 18 tiers including the lobes, each tier 50–120 µm long, with lateral cell-fusions but without lateral pit-connections. Cortical filaments 5–8 cells long, cells elongate-ovoid, 6–10 µm in diameter, with short epithallial cells. Genicula 130–240 µm long. Rhodoplasts discoid.
Reproduction. Gametangial thalli probably dioecious. Conceptacles slightly swollen, adaxial or terminal in the lobes with the pores opening on the upper edge or terminally. Carposporangial conceptacles unknown. Male conceptacles elongate, chamber narrow, spermatangia arising on the floor and walls. Tetrasporangial conceptacles swollen on the adaxial sides of the lobes, with the pore adaxial and usually subapical, lobe apices usually pointed (rarely rounded), chamber ovoid, 200–300 µm in diameter, tetrasporangia arising basally in the chamber, elongate-ovoid to clavate, 40–75 µm in diameter, zonately divided.
Distribution. Mauritius; South Africa; Philippines; Brazil. In Australia, from Swan River, W. Aust., to Coffs Harbour, N.S.W. Northern Aust.
[After Womersley, Mar. Benthic Fl. Southern Australia IIIB: 315–317 (1996)]
