Electronic Flora of South Australia Genus Fact Sheet

Genus PTEROSIPHONIA Falkenberg in Schmitz & Falkenberg 1897: 443.

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Pterosiphonieae

Thallus erect from terete prostrate filaments, bilaterally branched with simple or branched indeterminate axes bearing alternate, distichous, simple or branched, terete or compressed, determinate laterals 2–3 segments apart, with their bases coalescing with the main axis over one to a few segments. Trichoblasts usually absent apart from those bearing sex organs. Attachment by rhizoids on prostrate filaments. Structure. Apical cells single on indeterminate branches, dividing transversely or obliquely to form alternate laterals every 2–3 segments; pericentral cells 4–12 (5–9 in face view of compressed axes), ecorticate or corticate. Cells uninucleate.

Reproduction: Gametophytes dioecious, rarely with mixed phases. Procarps on modified trichoblasts; carposporophyte with a basal fusion cell and branched gonimoblast with clavate terminal carposporangia; cystocarps on determinate laterals, ovoid, pericarp ecorticate or corticate. Spermatangial organs borne on modified trichoblasts.

Tetrasporangia in determinate laterals, spirally arranged, single per segment, with 2 pre-sporangial and 1 post-sporangial cover cells.

Type species: P. cloiophylla (C. Agardh) Falkenberg in Schmitz & Falkenberg 1897: 443.

Taxonomic notes: A genus of some 19 species, the type studied in detail by Hommersand (1963, p. 261, figs 38–43). Pterosiphonia is characterised by its pinnate habit with the determinate laterals coalescing with the indeterminate axes over only a very few segments.

Only one species occurs on southern Australian coasts.

References:

HOMMERSAND, M.H. (1963). The morphology and classification of some Ceramiaceae and Rhodomelaceae. Univ. Calif. Pubis. Bot. 35(2), 165–366.

SCHMITZ, F. & FALKENBERG, P. (1897). Rhodomelaceae. In Engler, A. & Prantl, K., Die natürlichen Pflanzenfamilien. T.1. Abt. 2, pp. 421–480. (Englemann: Leipzig.)

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

Publication: Womersley, H.B.S. (24 February, 2003)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIID. Ceramiales – Delesseriaceae, Sarcomeniaceae, Rhodomelaceae
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIID 2003, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

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