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Electronic Flora of South Australia Genus Fact Sheet

Genus PTILOTHAMNION Thuret ex Le Jolis 1863: 118

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Spermothamnieae

Thallus usually minute, with prostrate filaments usually attached by digitate haptera, and erect, sparsely branched to pinnate, filaments or axes; most species epiphytic. Cells multinucleate.

Reproduction: Gametophytes monoecious or dioecious. Procarps subapical, with the upper two axial cells small and the subhypogenous cell larger, with 2 sterile periaxial cells and a supporting cell with a sterile apical cell and a lateral carpogonial branch. Auxiliary cell producing 2–5 gonimoblast initials which divide 1–3 times, the terminal or most cells becoming carposporangia; fusion cell slight to absent. Sterile procarp cells not dividing, but the hypogenous cell bearing, before or after fertilization, two branchlets which come to surround the carposporophyte. Spermatangial heads ovoid to elongate, sessile or pedicel late, terminal or lateral on erect filaments, composed of central axial cells, periaxial initials and surface spermatangia.

Tetrasporangia sessile or pedicellate on erect filaments, tetrahedrally or polyhedrally divided.

Type species: P. pluma (Dillwyn) Thuret in Le Jolis 1863: 118.

Taxonomic notes: A genus of 6–8 species (see Gordon 1972, pp 129, 135), with 2 species on southern Australian coasts, characterised by a female axis with 2 small cells, an outer involucre of two opposite branchlets from the larger hypogenous cell, no inner involucre from the sterile cells of the procarp, a single auxiliary cell, and the terminal or all cells of the gonimoblast becoming carposporangia.


GORDON, E.M. (1972). Comparative morphology and taxonomy of the Wrangelieae, Sphondylothamnieae and Spermothamnieae (Ceramiaceae, Rhodophyta). Aust. J. Bot. suppl. 4, 1–180.

Le JOLIS, A. (1863). Liste des algues marines de Cherbourg. Mém. Imp. Soc. Sci. Nat. Cherbourg 10, 1–168, Plates 1–6.

The Marine Benthic Flora of Southern Australia Part IIIC complete list of references.

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (24 December, 1998)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIC. Ceramiales – Ceramiaceae, Dasyaceae
©State Herbarium of South Australia, Government of South Australia


1. Erect filaments 15–20 µm in diameter, prostrate filaments 15–30 (–40) µm in diameter; involucral filaments developing on hypogenous cell after fertilization; carposporangia in successive gonimolobes; spermatangial heads terminal; tetrasporangia pedicellate; epiphytic on Zonaria

P. schmitzii

1. Erect filaments 30–60 µm in diameter, prostrate filaments 25–35 µm in diameter; involucral filaments present on hypogenous cell before fertilization; carposporangia in gonimolobes developing simultaneously; spermatanigal heads lateral, sessile; tetrasporangia sessile; epiphytic on Lenormandia

P. subsimplex

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