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Electronic Flora of South Australia Genus Fact Sheet

Genus PTILOCLADIA Sonder 1845: 52

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Crouanieae

Thallus erect, much branched irregularly radially with lateral branches arising from the basal cell of whorl-branchlets, axial cells with 4 equal length whorl-branchlets branched several times, the whorls either covering the axis or separated and exposing the axial cells; axes of branches densely, slightly or not covered by corticating rhizoids originating from the basal cells of whorl-branchlets and descending within the gelatinous sheath of the axial cells; lateral branches arising from basal cells of whorl-branchlets, 2–5 cells long before whorl-branchlet initiation; pyriform gland cells present or absent; attachment by rhizoids. Cells uninucleate.

Reproduction: Gametophytes dioecious. Procarps borne on the basal cell of whorl-branchlets which may or may not have further cells, with a supporting cell bearing a 4-celled carpogonial branch. Post-fertilization the auxiliary cell cuts off an upper cell which extends horizontally and produces 2 lateral gonimolobes, all cells becoming carposporangia, and often later gonimolobes. The carposporophyte is protected by enlarged and surrounding adjacent whorl-branchlets. Spermatangia are cut off via initials from the outer cells of whorl-branchlets.

Tetrasporangia are borne on mid cells of whorl-branchlets, sessile, ovoid to subspherical, tetrahedrally divided.

Type species: P. pulchra Sonder 1845: 52.

Taxonomic notes: A genus of 7 species, 5 from southern Australia (Wollaston 1968, p. 254 and below), P. japonica Itono (1977, p. 15) from Japan and P. yuenii Abbott in Abbott & Norris (1993, p. 452) from the Hawaiian Islands.


ABBOTT, I.A. & NORRIS, R.E. (1993). New species of Ceramiaceae (Rhodophyta) from the Hawaiian Islands. Phycologia 32, 451–461.

ITONO, H. (1977). Studies on the Ceramiaceous algae (Rhodophyta) from southern parts of Japan. Bibliotheca Phycologia 35, 1–499.

SONDER, O.G. (1845). Nova Algarum genera et species, quas in itinere ad oras occidentales Novae Hollandiae, collegit L. Preiss, Ph.Dr. Bot. Zeit. 3, 49–57.

WOLLASTON, E.M. (1968).Morphology and taxonomy of southern Australian genera of Crouanieae Schmitz (Ceramiaceae, Rhodophyta). Aust. J. Bot. 16, 217–417.

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

Author: E.M. Wollaston & 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. Thallus relatively robust (lower branches 1–2 mm in diameter), clothed with closely adjacent whorls of whorl-branchlets from the apices down, densely corticated with rhizoidal filaments within the gelatinous sheath of the axial cells; whorl-branchlets with terminal rows of 2–3 subspherical to ovoid cells


1. Thallus slender (lower branches 0.5–1 mm in diameter), with the whorl-branchlet whorls mostly separated and exposing the axial cells between them, cortication absent or slight and starting well below the branch apices; whorl-branchlets with single, elongate (L/D 1.5–2.5) terminal cells


2. Cortication on older branches forming an inner layer of larger cells and outer layer of smaller cells, with occasional anticlinal filaments; gland cells absent on whorl- branchlets; carposporophytes in short lateral branches

P. pulchra

2. Cortication on older branches by rhizoids from the basal cells of whorl-branchlets with rows of cells lying along the axis and short outward branches; gland cells on whorl-branchlets present, often plentiful near branch tips; carposporophytes situated along elongate branches

P. vestita

3. Thallus mostly ecorticate, whorls of whorl-branchlets separated throughout thallus, gland cells present

P. australis

3. Thallus corticated below, whorls of whorl-branchlets distinctly to slightly separated, gland cells present or absent


4. Cortication relatively loose, spreading from the nodes, filaments largely outside the axial cell wall sheath; gland cells absent; tetrasporangia large, 80–100 µm in diameter

P. gracilis

4. Cortication compact, of appressed filaments within the axial cell wall sheath; gland cells present; tetrasporangia small, 20–30 µm in diameter

P. crouanioides

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