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Phylum Phaeophyta – Order Chordariales

Thallus (sporophyte) 2–50 cm long, erect, cylindrical, usually much branched, slightly to moderately mucoid, solid or becoming hollow, with a small discoid holdfast, epiphytic or epilithic. Branches haplostichous, composed of a medulla of a single axial filament or of 4–5 filaments, the latter as a core or becoming separated, producing close to the apices primary assimilatory filaments which usually persist and may form a layer (rudimentary or well developed) over the thallus or become separated by enlargement of cortical cells; some may be lost from older branches. Cortex formed by radial and lateral divisions of basal cells of primary assimilatory filaments, becoming 2–4 cells thick and usually pseudoparenchymatous, with tufts of secondary assimilatory filaments developing in most genera from outer cortical cells adjacent to the primary filaments; such tufts often at first related to the axial cells and their derivatives and thus more or less in whorls, later obscured by development of further secondary tufts. Outer cells each with several phaeoplasts, each with a pyrenoid. Phaeophycean hairs present on the basal cells of primary assimilatory filaments and in the secondary tufts. Growth of the branches apical, directly from the single or group of 4–5 apical cells.

Reproduction: Reproduction by uniseriate plurilocular sporangia producing mitospores and by ovoid unilocular sporangia producing meiospores or mitospores, both borne at the base of secondary assimilatory filaments and often on the one plant. Gametophytes filamentous, isogamous.

Life history diplohaplontic, with a diploid macrothallus and a haploid gametophytic microthallus, in some taxa with a diploid plethysmothallus.

Taxonomic notes: A family of 5 genera (Kylin 1940, pp. 45–53), with four genera known from southern Australia.


KYLIN, H. (1940). Die Phaeophyceenordnung Chordariales. Acta Univ. lund. N.F. Avd. 2, 36(9), 1–67, Plates 1–8.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
Part II
©Board of the Botanic Gardens and State Herbarium, Government of South Australia


1. Apices with a group of 4–5 apical cells (largely obscured by primary assimilatory filaments), producing a medulla of 4–5 filaments which become separated laterally leaving a hollow central part in older branches


1. Apices with a single apical cell and a single axial filament throughout the thallus


2. Primary assimilatory filaments persistent, 8–20 cells long, covering the thallus


2. Primary assimilatory filaments short, 1–5 cells long, either becoming separated, leaving a bare and relatively smooth outer cortex between the secondary tufts, or covering the surface but short (mostly 1–2 celled) and papillose


3. Outer cortex relatively smooth and bare between the secondary tufts


3. Outer cortex papillose, covered by rudimentary primary assimilatory filaments of 1–2 (–3) ovoid cells


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