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Electronic Flora of South Australia Genus Fact Sheet

Genus HAPLODASYA Falkenberg in Schmitz & Falkenberg 1897: 474

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Lophothalieae

Thallus erect, radially branched either profusely or with occasional laterals, with terete, corticated branches from close to the apices. Pericentral cells 5 (rarely 4), formed in alternating sequence, each segment with a persistent, rhodoplastic monosiphonous trichoblast; cortical cells in H. tomentosa producing simple adventitious filaments. Attachment by cellular masses in the host conceptacles; epiphytic on species of Cystophora or Carpoglossum. Structure monopodial, developing trichoblasts close to apices on a 1/5 spiral and pericentral cells in alternating sequence; trichoblasts basally branched, with long unbranched ends, adventitious filaments with small basal cells and upper cells similar to those of trichoblasts. Cells uninucleate.

Reproduction: Gametophytes dioecious. Procarps borne on segments (which become polysiphonous) at the base of trichoblasts or adventitious filaments, with the fifth pericentral cell producing a sterile group of cells and a 4-celled carpogonial branch; the fertilised carpogonium cuts off 2 connecting cells. Carposporophyte with a basal fusion cell and branched gonimoblast with clavate terminal carposporangia. Cystocarps ovoid to urceolate; pericarp ostiolate with about 12 erect filaments, each cell cutting off outer cells and 1–2 cortical layers. Spermatangial organs borne on unbranched ends of trichoblasts or short adventitious filaments, with 1–2 sterile apical cells, without trichoblasts themselves, axial cells with 3 pericentral cells forming an inner layer of initials and outer of spermatangia.

Tetrasporangia borne in stichidia formed from unbranched ends of trichoblasts or the adventitious filaments, without bearing trichoblasts, with 4 pericentral cells (the second of which forms a tetrasporangium) which occur in a straight longitudinal row, with 2 pre-sporangial and 1 post-sporangial cover cells.

Type species: H. reinboldii Falkenberg (1897, p. 475) = H. urceolata (Harvey ex J. Agardh) Parsons 1975: 672.

Taxonomic notes: A genus of 2 species, monographed by Parsons (1975). While reproductive features, especially the stichidia and spermatangial organs, are similar in both species, they differ significantly in that H. tomentosa produces abundant adventitious filaments but H. urceolata does not.

Silva et al. (1996, p. 440) include Haplodasya under the Dasyaceae, probably inadvertently as Parsons (1975) clearly showed its relationships are with the Lophothalieae.


PARSONS, M.J. (1975). Morphology and taxonomy of the Dasyaceae and Lophothalieae (Rhodomelaceae) of the Rhodophyta. Aust. J. Bot. 23(4), 549–713.

SCHMITZ, F. & FALKENBERG, P. (1897). Rhodomelaceae. In Engler, A. & Prantl, K., Die natürlichen Pflanzenfamilien. T.1. Abt. 2, pp. 421–480. (Englemann: Leipzig.)

SILVA, P.C., BASSON, P.W. & MOE, R.L. (1996). Catalogue of the Benthic Marine Algae of the Indian Ocean. (Univ. California Press: Berkeley.)

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

Author: H.B.S. Womersley & M.J. Parsons

Publication: Womersley, H.B.S. (24 February, 2003)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIID. Ceramiales – Delesseriaceae, Sarcomeniaceae, Rhodomelaceae
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIID 2003, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.


1. Thallus pyramidal, much branched, adventitious filaments absent from the cortex

H. urceolata

1. Thallus of elongate branches, adventitious filaments profuse on the cortical cells

H. tomentosa

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