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Electronic Flora of South Australia
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Electronic Flora of South Australia Genus Fact Sheet

Genus CROUANIA J. Agardh 1842: 83

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Crouanieae

Thallus erect, often from prostrate basal filaments, much branched with lateral branches arising from axial cells below apices and basal cells of whorl-branchlets and often developing more strongly, axial cells each with 3 whorl-branchlets branched 4–8 times and covering the axis or with axial cells exposed between whorls; laterals 10–20 cells long before initiation of whorl-branchlets; attachment by rhizoidal holdfasts; gland cells absent. Cells uninucleate.

Reproduction: Gametophytes dioecious. Procarps borne in place of whorl-branchlets near branch apices, with a supporting cell bearing a 4-celled carpogonial branch. Post-fertilization the auxiliary cell cuts off a terminal and then lateral gonimolobes, the carposporophyte being surrounded by whorl-branches in a rounded to clavate end of a branch. Spermatangia are cut off from outer cells of whorl-branchlets.

Tetrasporangia are borne on basal cells of whorl-branchlets, sessile, subspherical, tetrahedrally divided.

Type species . C. attenuata (C. Agardh) J. Agardh 1842: 83.

Taxonomic notes: A genus of numerous species, world-wide in distribution.


AGARDH, J.G. (1842). Algae Maris Mediterranei et Adriatici, Observationes in Diagnosin Specierum et Dispositionem Generum. (Fortin, Masson: Paris.)

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 slimy, enveloped in mucilage. Terminal cells of whorl-branchlets small, rounded

C. mucosa

1. Thallus not slimy, gelatinous sheath contouring axes and whorl-branchlets at least in mature to older parts of thallus. Terminal cells of whorl-branchlets rounded or elongate


2. Plants less than 4 cm high. Erect axes arising from a prostrate base. Terminal cells of whorl-branchlets mostly rounded, L/D 1–2


2. Plants 3–15 cm high. Erect axes attached to substrate by rhizoids. Terminal cells of whorl-branchlets elongate, L/D (2–) 3–4 (–6)


3. Axial cells elongate, not increasing in L/D in central to lower thallus. Whorl-branchlet whorls becoming separated at maturity to form distinct rings; lower whorl-branchlets some times shorter

C. shepleyana

3. Central to lower cells of older axes often larger with increased L/D. Whorl-branchlets near-horizontal, outer part spreading and touching or almost so in adjacent whorls

C. destriana

4. Thallus usually 4–15 cm high. Whorl-branchlets (150–) 200–300 (–400) µm long, horizontal to slightly upwardly directed (form sometimes distorted by growth conditions, presence of epiphytes or preservation). Axial cells clearly visible throughout. Whorl-branchlets usually adjacent or almost so

C. robbii

4. Thallus up to 4 cm high. Whorl-branchlets 200–450 µm long usually with their outer part directed upwards. Axes slender with widely separated whorls of whorl-branchlets

C. brunyana

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