Electronic Flora of South Australia Genus Fact Sheet

Genus HECATONEMA Sauvageau 1897: 248

Phylum Phaeophyta – Order Dictyosiphonales – Family Punctariaceae

Thallus minute, filamentous and heterotrichous, with a basal disc of more or less compact, branched, radiating filaments, uniseriate but with frequent intercalary longitudinal divisions mostly parallel to the substratum, and erect, simple or usually branched, filaments from many but not all the disc cells, with occasional intercalary longitudinal divisions (especially where branches occur); sheathed phaeophycean hairs frequent, terminal or lateral on erect filaments; ascocysts present in some species. Cells with several discoid phaeoplasts, each with a pyrenoid.

Reproduction: Reproduction by lanceolate to elongate-ovoid, multiseriate, plurilocular sporangia, producing zooids which reproduce the filamentous thallus directly, or which may give rise to parenchymatous thalli (of the Punctariaceae). Some species with unilocular sporangia (Loiseaux 1970).

Type species: H. maculans (Collins) Sauvageau.

Taxonomic notes: A genus of about 10 species (Pedersen 1984, p. 71), usually epiphytic, which are probably largely microthallic stages in the life histories of parenchymatous genera of the Punctariaceae, especially of Punctaria and Asperococcus (Clayton 1974, p. 793; Pedersen 1984, p. 60). Hecatonema has previously been placed in the Ectocarpaceae (e.g. Cardinal 1964, p. 75) or the Myrionemataceae (e.g. Loiseaux 1970). It is treated here as an independent genus pending further studies of Punctariaceae life histories in southern Australia.

References:

CARDINAL, A. (1964). Étude sur les Ectocarpacees de la Manche. Nova Hedwigia 15, 1–86, Figs. 1–41.

CLAYTON, M.N. (1974). Studies on the development, life history and taxonomy of the Ectocarpales (Phaeophyta) in southern Australia. Aust. J. Bot. 22, 743–813.

LOISEAUX, S. (1970). Notes on several Myrionemataceae from California using culture studies. J. Phycol. 6, 248–260.

PEDERSEN, P.M. (1984). Studies on primitive brown algae (Fucophyceae). Opera Bot. 74, 1–76.

SAUVAGEAU, C. (1897). Sur quelques Myrionemacees. Ann. Sci. nat.(Bot.), Ser. 8, 5, 161–288.

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
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