Electronic Flora of South Australia Genus Fact Sheet

Genus HELMINTHOCLADIA J. Agardh 1852: 412, nom. cons.

Phylum Rhodophyta – Class Florideophyceae – Order Nemaliales – Family Liagoraceae

Thallus (gametophyte) usually much and variously branched, multiaxial with a medulla of fairly slender filaments and a cortex of subdichotomous filaments, usually with distinctly larger, ovoid or pyriform, terminal cells, or at least not with markedly smaller terminal cells.

Tetrasporophyte minute, filamentous or discoid, known only in H. calvadosii in culture (Boillot 1974, p. 187, pl. 1).

Reproduction: Carpogonial branches lateral, curved, 3- or 4-celled with a short conical carpogonium. Zygote usually segmenting obliquely, with the segments producing the carposporophyte. Sterile post-fertilization filaments irregularly developed from cells adjacent to supporting cell, forming an involucre around the carposporophyte, but not a distinct tuft of descending rhizoidal filaments.

Tetrasporangia terminal on filaments, cruciately divided.

Life history (where known) triphasic with macroscopic gametophytes and minute tetrasporophytes.

Type species: H. purpurea (Harvey) J. Agardh 1852: 414 [= H. calvadosii (Lamouroux ex Duby)Setchell].


AGARDH, J.G. (1852). Species Genera et Ordines Algarum. Vol. 2, Part 2, pp. 337–720. (Gleerup: Lund.)

BOILLOT, A. (1974). Le sporophyte de l'Helminthocladia calvadosii (Lamouroux)Setchell (Rhodophycée, Nemalionale). Le Botaniste 56, 187–192.

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.


1. Thallus less than 7 cm high, with several subdichotomous fronds arising from a relatively massive base; fronds with laterals only near their base

H. dotyi

1. Thallus usually 10–30 cm high, with numerous lateral branches above


2. Thallus with one to several simple or rarely branched axes, profusely covered with short, mostly simple, laterals up to 1 cm long

H. beaugleholei

2. Thallus with branched axes and strongly developed, usually irregular, branched laterals mostly over 1 cm long


3. Axes subdichotomous with wide axils, densely covered with subdichotomous laterals, 0.5–3 cm long, forming a dense, bushy thallus. Terminal cells of cortical filaments 15–20 (–25) µm long, not markedly larger than subterminal cells

H. densa

3. Thallus with irregularly and usually much-branched axes and laterals. Terminal cells of cortical filaments usually 30–60 µm long, often markedly larger than subterminal cells

H. australis

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