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Electronic Flora of South Australia Genus Fact Sheet

Genus HYPNEOCOLAX Boergesen 1920: 479

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Hypneaceae

Thallus white to pale red, 0.2–2 mm high, with a short basal stalk attached to the host and a globular head with radial lobes; parasitic on various species of Hypnea. Structure uniaxial, apical cell inconspicuous, with an axial filament in each lobe; medulla of ovoid cells with numerous secondary pit-connections, cortex 1–3 cells thick.

Reproduction: Thalli monoecious or dioecious; procarpic and monocarpogonial. Carpogonial branches 3-celled, borne outwardly on an inner cortical cell. Auxiliary cells intercalary, next outwardly to the supporting cell. Gonimoblast initial single, formed outwardly, producing filaments in a reticulum, the outer cells establishing pit-connections with inner pericarp cells and cells of the reticulum forming clusters of small cells which cut off single, ovoid, carposporangia. Cystocarps protruding from the parent lobe, pericarp 1–4 cells thick, non-ostiolate. Spermatangia cut off in short chains, via initials, from outer cortical cells.

Tetrasporangia cut off from outer cortical cells in sori, zonately divided into bisporangia or tetrasporangia.

Life history triphasic with isomorphic gametophytes and tetrasporophytes.

Type species: H. stellaris Boergesen 1920: 479, figs 433–435.

Taxonomic notes: Hypneocolax is widely distributed on various species of Hypnea, with only a single species recognised, with two forms: the type form, f. stellaris, with bisporangia, from the West Indies, and f. orientalis Weber-van Bosse (1928, p. 393, fig. 143) from Indonesia, with tetrasporangia. The southern Australian specimens agree with the latter form (considered below as a subspecies).

The reproduction of Hypneocolax has been investigated by Fan (1961).


BOERGESEN, F. (1920). The marine algae of the Danish West Indies. Part 3. Rhodophyceae. Dansk bot. Ark. 3, 369–504.

FAN, K.C. (1961). Morphological studies of the Gélidiales. Univ. Calif. Pubis Bot. 32, 315–368.

WEBER-VAN BOSSE, A. (1928). Liste des Algues du Siboga. IV. Rhodophyceae. Part 3. Gigartinales and Rhodymeniales. Siboga-Expeditae, Monogr. LIXd, pp. 393–533, Plates 11–16.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 January, 1994)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIA, Bangiophyceae and Florideophyceae (to Gigartinales)
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIA 1994, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

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