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Electronic Flora of South Australia Genus Fact Sheet

Genus GIRAUDIA Derbés & Solier 1851: 100

Phylum Phaeophyta – Order Dictyosiphonales – Family Giraudiaceae

Thallus pulvinate, 2–10 mm high. Basal plate monostromatic, of radiating filaments, producing erect, large celled, medullary filaments 1-several cells long, from which free, relatively stout, erect axes arise. Erect axes each with a basal, uniseriate meristem, and above with tiers each of 5–16 cells, then tapering to the apex; cells of axes with numerous discoid phaeoplasts, each with a pyrenoid. Phaeophycean hairs terminal and lateral.

Microthallus discoid, with prostrate radiating filaments bearing erect filaments, ascocysts, phaeophycean hairs and plurilocular sporangia.

Reproduction: Reproduction of macrothallus by plurilocular sporangia of three types: discrete, borne on short pedicels from upper medullary cells or from erect axes; in clusters on erect axes; and developed by subdivision of cells of erect axes, forming immersed sori. Unilocular sporangia (only known in G. robusta) elongate-ovoid, pedicellate, borne on upper medullary cells.

Life history direct from each type of zooid.

Type species: G. sphacelarioides Derbés & Solier.

Taxonomic notes: A genus of two species, the type and G. robusta Skinner & Womersley from southern Australia.

References:

DERBÉS, A. & SOLIER, A.J.J. (1851). Algues. In Castagne, J.L.M., Supplément au Catalogue des plantes qui croissent naturellement aux environs de Marseille. pp. 93–121. (Nicot & Pardigon: Aix.)

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

KEY TO SPECIES OF GIRAUDIA

1. Erect axes with tiers of 10–12 (–15) cells, each oblong in face view, tapering to an apex bearing a cluster of 2–6 phaeophycean hairs; basal plurilocular sporangia often branched, with clusters of multiseriate plurilocular sporangia and uniseriate sporangia in intercalary sori on the upper part of erect axes

G. sphacelarioides

1. Erect axes with tiers of 5–7 (–9) cells, becoming slightly six-sided on mature parts in face view, tapering to a uniseriate apex bearing laterals with plurilocular sporangia, and with a terminal phaeophycean hair; simple, basal, plurilocular sporangia and unilocular sporangia present

G. robusta


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