Electronic Flora of South Australia Family Fact Sheet


Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales

Thallus erect, much branched, with long axes and lateral branches bearing two distichous (3 or 4 in P. tristichus) rows of short determinate ramuli of similar length.

Structure uniaxial, with each axial cell producing four pericentral cells of which the two lateral ones develop alternately into the ramuli; medulla of axial filaments and rhizoids, cortex pseudoparenchymatous, with secondary pit-connections between inner cells.

Reproduction: Sexual thalli usually dioecious; procarpic and usually bicarpogonial. Carpogonial branches 2-celled, borne in dense fertile clusters usually on the lower side of a lateral filament, each cluster including a distinctive intercalary cell which becomes the auxiliary cell and (1–) 2 carpogonial branches, as well as sterile filaments. Gonimoblast developing outwardly, with a basal fusion cell producing filaments which terminate in single or two-celled chains of small carposporangia. Cystocarps protuberant, sessile or more usually stalked, pericarp bilabiate, thick and of small cells, with an elongate ostiole. Spermatangial nemathecia sessile or stalked, ovoid, borne between the ramuli or on the rachis, with the spermatangia cut off from initials within flask-shaped or laterally elongate pits.

Tetrasporangial nemathecia sessile or stalked, ovoid, lying between the ramuli or on the rachis, tetrasporangia formed in cavities within the nemathecium, small, zonately divided.

The Phacelocarpaceae contains only the genus Phacelocarpus. It was studied in detail by Searles (1968), and Stenocladia and Nizymenia (included by Searles) have been placed in a separate family by Womersley (1971b). Two misplaced names are Phacelocarpus densus Areschoug (1854, p. 347) which is Areschougia congesta, and Phacelocarpus echionotus J. Agardh (1899, p. 92) which is Rhodocallis elegans Kützing.

Life history triphasic with isomorphic gametophytes and tetrasporophytes.


AGARDH, J.G. (1899). Analecta Algologica. Cont. V. Acta Univ. lund. 35, 1–160, Plates 1–3.

ARESCHOUG, J.E. (1854). Phyceae novae et minus cognitae in maribus extraeuropaeis collectae. Ups. Soc. Sci. nova Acta, Ser. III, 1, 329–72.

SEARLES, R.B. (1968). Morphological studies of red algae of the order Gigartinales. Univ. Calif Pubis Bot. 43, vi + 1–86, Plates 1–12.

WOMERSLEY, H.B.S. (1971b). The relationships of Nizymenia and Stenocladia (Gigartinales, Rhodophyta). Phycologia 10, 199–203.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 January, 1994)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIA, Bangiophyceae and Florideophyceae (to Gigartinales)
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIA 1994, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

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