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Phylum Phaeophyta – Order Dictyosiphonales

Thallus (sporophyte) unbranched, usually 5–50 cm high, membranous, complanate, ligulate to ovoid and solid or hollow, or terete to inflated and bullate and hollow. Growth initially from a trichothallic filament, soon becoming polystichous with diffuse divisions. Structure of a small-celled phaeoplastic cortex and medulla of cells of similar size or much larger. Phaeophycean hairs scattered.

Microthallus (often gametophytes) minute, filamentous, branched, usually with occasional intercalary longitudinal divisions (otherwise recognised as Streblonema or Hecatonema). Life history diplohaplontic or direct via the microthallus.

Reproduction: Sporophyte with plurilocular and unilocular sporangia, transformed from cortical cells and swollen, or exserted from the cortex.

Taxonomic notes: A family of numerous genera (Wynne 1982, p. 122), with two present on southern Australian coasts, together with Hecatonema. The microthallic stages correspond to taxa of Streblonema (Ectocarpaceae) and Hecatonema (see below), and can only be clarified by further culture studies, few of which have been reported in southern Australia.


WYNNE, M.J. (1982). Phaeophyceae. In Parker, S.P. (Ed.), Synopsis and classification of living organisms, Vol. I, pp. 115–125. (McGraw-Hill: New York.)

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. Thallus 0.5–2 mm high and across, branched, with uniseriate or occasionally biseriate filaments bearing multiseriate plurilocular sporangia


1. Thallus usually over 2 cm high and 0.5–6 cm broad, inflated or compressed, polystichous throughout


2. Thallus complanate, solid, (2–) 4–6 cells thick, 1–6 cm broad, with surface cells mostly similar in size to inner cells; plurilocular and unilocular sporangia developed from cortical cells, scattered, not or slightly protruding


2. Thallus hollow, irregularly terete or bullate, or compressed with the sides closely adjacent, 0.5–5 cm across, with the cortical cells distinctly smaller than the inner medullary cells; sporangia in sori with phaeophycean hairs, exserted from the cortex


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