Electronic Flora of South Australia Genus Fact Sheet

Genus PTILONIA (Harvey) J. Agardh 1852: 773

Phylum Rhodophyta – Class Florideophyceae – Order Bonnemaisoniales – Family Bonnemaisoniaceae

Thallus erect, much branched essentially complanately with alternate, compressed, branches, tapering slightly from base to rounded apices, margins entire, axes thickened below; holdfast discoid. Structure uniaxial with an inconspicuous apical cell and the subapical cells each cutting off two pairs of periaxial cells, the first two at right angles with the lateral one developing into a longer filament, then a second pair with the lateral opposite the first longer lateral remaining shorter; the transverse periaxial cells contribute to the cortex. Cortex pseudoparenchymatous, of rounded cells with adjacent air spaces, with a prominent axial filament throughout becoming surrounded by a layer of small (rhizoidal) cells; outer cortex with larger, usually clear, slightly sub-surface, gland cells. Older axes thickened, at first centrally, by a cortical meristem.

Reproduction: Gametangial thalli monoecious or dioecious. Carpogonial branches 3-celled, borne near branch tips or on short laterals on periaxial (supporting) cells. Gonimoblast filaments arising from the fertilized carpogonium (or hypogynous cell), developing a basal fusion cell and a dense, much branched, erect to spreading tuft bearing terminal clavate to ovoid carposporangia. Pericarp thick, ostiolate with short, branched, filaments lining the pore. Cystocarps ovoid, sessile or stalked. Spermatangia in sort over ends of branches, cut off via initials from outer cortical cells.

Life history apparently biphasic, with the gametophytes arising from a crustose stage; tetrasporophytes unknown.

Type species: P. magellanica (Montagne) J. Agardh 1852: 774.

Taxonomic notes: Ptilonia includes six species, two from southern Australia, two from New Zealand (Bonin & Hawkes 1988b), one (the type) from the subantarctic and one from Japan (Chihara & Yoshizaki 1978). Ptilonia was first described as a section of Plocamium by Harvey (1847, p. 124). Chihara & Yoshizaki (1978) considered Ptilonia was not distinct from Delisea, but this was refuted by Bonin & Hawkes (1988b). Ptilonia differs from Delisea in habit, having entire, smooth margined, branches in contrast to the dentate or spinose branches of Delisea, resulting from the lateral adhesion of the determinate laterals in the former.

References:

AGARDH, J.G. (1852). Species Genera et Ordines Algarum. Vol. 2, Part 2, pp. 337–720. (Gleerup: Lund.)

BONIN, D.R. & HAWKES, M.W. (1988b). Systematics and life histories of New Zealand Bonnemaisoniaceae (Bonnemaisoniales, Rhodophyta): III. The genus Ptilonia. N.Z. J. Bot. 26, 633–644.

CHIHARA, M. & YOSHIZAKI, M. (1978). Anatomical and reproductive features of Ptilonia okadai (Rhodophyta, Bonnemaisoniaceae). Phycologia 17, 382–387.

HARVEY, W.H. (1847). Nereis Australis, pp. 1–64, Plates 1–25. (Reeve: London.)

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (28 June, 1996)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIB. Gracilarialse, Rhodymeniales, Corallinales and Bonnemaisoniales
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIB 1996, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

KEY TO SPECIES OF PTILONIA

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