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Electronic Flora of South Australia Genus Fact Sheet

Genus STREPSITHALIA Bornet ex Sauvageau 1896a: 64

Phylum Phaeophyta – Order Chordariales – Family Leathesiaceae

Thallus less than 2 mm long, with endophytic, sometimes stoloniferous, branched medullary filaments, with or without short, erect medullary filaments only a few cells long within the host cortex, producing erect, determinate, cortical filaments outside the host cortex. Cortical assimilatory filaments 4–12 (–20) cells long, of fairly uniform height, simple or basally branched, usually with a gelatinous matrix around individual or clusters of erect filaments. Cells with 2–4 phaeoplasts, each with a pyrenoid. Phaeophycean hairs arising from medullary filaments.

Reproduction: Plurilocular sporangia short, uniseriate or occasionally biseriate, with 3–8 locules, borne singly or in small clusters on upper medullary cells. Unilocular sporangia sessile or with a unicellular pedicel, lateral on prostrate or erect medullary filaments.

Type species: S. curvata Sauvageau.

Taxonomic notes: Strepsithalia is an ill-defined genus of some 6 species, known from Europe and from southern Australia, and probably more widespread on temperate coasts.

The position of Strepsithalia is uncertain, and it is here regarded as a simple, possibly reduced, member of the Leathesiaceae because of the slight development of erect medullary filaments, the small clusters of determinate cortical filaments usually with associated mucilage, the presence of phaeophycean hairs and the uniseriate plurilocular sporangia. Some authors (e.g. Hamel 1939b, p. xx) have placed Strepsithalia in the Myrionemataceae, while Fritsch (1945, p. 89) considered it a reduced form with affinity to the Mesogloiaceae (Chordariaceae). The life history of Strepsithalia and its possible relationships to larger taxa are virtually unknown. The following account of three species on southern Australian coasts is provisional and further detailed studies are needed.


FRITSCH, F.E. (1945). The structure and reproduction of the Algae. Vol. II. (Univ. Press: Cambridge.)

HAMEL, G. (1939b). Phéophycées de France. Fasc. V, pp. 337–432, i-xlvii. (Paris.)

SAUVAGEAU, C. (1896a). Note sur le Strepsithalia. J. de Bot. 10, 53–65.

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

Author: H.B.S. Womersley & S. Skinner

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. Determinate cortical filaments simple, cylindrical to very slightly clavate, 3–6 µm in diameter with cells below L/B 4–6, and above L/B (1–) 2–3; on Liagora (or Helminthocladia)

S. liagorae

1. Determinate cortical filaments simple or branched, almost cylindrical, 6–14 µm in diameter with cells L/B less than 2; on Leathesia or Helminthocladia


2. Determinate cortical filaments simple, 120–200 µm long, 10–14 µm in diameter; on Leathesia

S. leathesiae

2. Determinate cortical filaments usually basally branched, 40–80 µm long, 6–8 Aim in diameter; on Helminthocladia

  3 S. aemula

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