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Electronic Flora of South Australia Genus Fact Sheet

Genus ANTITHAMNIONELLA Lyle 1922: 347

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Heterothamnieae

Thallus usually with prostrate axes attached by haptera, and erect lateral axes with long (sometimes short) series of small subapical cells and whorls of 2–4 (–6) simple or branched whorl-branchlets from each axial cell, often more branched near thallus base, with the basal cells usually not branched (except in Aa glandifera) and smaller or similar in size to the next outer cell; gland cells usually present, sessile, usually single on second to fifth cell of whorl-branchlets, numerous in some species, touching only the bearing cell or sometimes also the next outer cell. Lateral branches produced in place of a whorl-branchlet or developing on the basal cell of a whorl-branchlet. Cells uninucleate.

Reproduction: Gametophytes dioecious or monoecious. Procarps 1–3 near branch apices, borne on normal or reduced whorl-branchlets with the basal cell acting as the supporting cell of a 4-celled carpogonial branch and usually bearing only one further cell; the fertile axial cell usually lacks other whorl-branchlets. Carposporophyte usually terminal, with axial growth continued by laterals from below, and surrounded by lateral branches or whorl-branchlets from below. Spermatangia cut off from initials formed laterally on short axes borne adaxially on rachis cells of whorl-branchlets.

Tetrasporangia sessile on lower cells of whorl-branchlets, subspherical to ovoid, tetrahedrally or subdecussately divided.

Type species: A. sarniensis Lyle 1922: 348, figs 1–4.

Taxonomic notes: Wollaston (1968, p. 339) recognised Antithamnionella as a distinct genus on vegetative features (such as inconsistency in number and branching of whorl-branchlets, and position of gland-cells on normal whorl-branchlets) as well as tetrahedrally divided tetrasporangia. Athanasiadis (1996, p. 101) also recognised it as a distinct genus and suggests it contains some 19 species. However, he considered the genus is not monophyletic and found no characters that could be considered distinctive for the genus. Clearly Antithamnionella is one of the least well defined genera of the tribe and much further study is needed.


ATHANASIADIS, A. (1996). Morphology and classification of the Ceramioideae (Rhodophyta) based on phylogenetic principles. Opera Botanica No. 128, pp. 1–216.

LYLE, L. (1922). Antithamnionella, a new genus of algae. J. Bot. Lond. 60, 346–350.

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: H.B.S. Womersley & E.M. Wollaston

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. Whorl-branchlets in close whorls of 5–6

Aa multiramosa

1. Whorl-branchlets in separated whorls of 2–4 (–5)


2. Whorl-branchlets in whorls of (2–) 3–4, with their basal cells distinctly shorter than the next cell(s). Carposporophyte producing up to 7 ovoid to elongate groups of carposporangia

Aa ternifolia

2. Whorl-branchlets in whorls of 1–2 (–3), basal cells as long as the next cell. Carposporophyte seldom producing more than 3 rounded groups of carposporangia


3. All whorl-branchlets usually unbranched; gland cells sessile on upper side of 2nd or 3rd cell of whorl-branchlet, more abundant in upper parts of plant

Aa spirographidis

3. Whorl-branchlets becoming branched with (2–) 3–5 alternate laterals; gland cells numerous (up to 20) on whorl-branchlets, most abundant in lower parts of plants

Aa glandifera

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