Electronic Flora of South Australia Genus Fact Sheet

Genus WILSONAEA Schmitz 1893: 231

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Uncertain

Thallus erect, radially branched, branches bearing apical tufts of monosiphonous filaments but denuded below. Structure. Apices monopodial, with monosiphonous filaments several cells long, lower cells producing lateral monosiphonous branches in a 1/4 spiral and cutting off 4 (–5) pericentral cells each of which divides transversely into 2. Axes soon become corticated with rhizoids between the pericentral cells and an extensive parenchymatous cortex. The monosiphonous branches have adherent basal walls at the dichotomies and the lower segments become polysiphonous, and their cells are rhodoplastic.

Reproduction: Gametophytes dioecious. Procarps on several successive segments of special polysiphonous branches below terminal tufts, with a 4-celled carpogonial branch. Carposporophytes with a basal branched fusion cell and branched gonimoblast with terminal carposporangia. Cystocarps lateral and terminal on short branches, corticated. Spermatangia covering lower monosiphonous cells of the laterals, with an outer layer of spermatangia from a layer of initials produced by pericentral cells.

Stichidia robust, borne near ends of lesser branches, with whorls of 4–5 pericentral cells and 3–4 tetrasporangia, each with 3 cover cells and an outer cortical layer.

Type (and only) species: W. dictyuroides (J. Agardh) Schmitz 1893: 231.

Taxonomic notes: The position of Wilsonaea was considered by Schmitz (1923, p. 231) as possibly closest to Bostrychia, which it resembles in the transversely divided pericentral cells, position of carpogonial branches and whorls of tetrasporangia. Falkenberg (1901, pp. 527–531) related it to both the Dasyaceae and Bostrychia. Kylin (1956, p. 555) considered it as probably a member of the Dasyaceae. The monopodial development, rhodoplastic monosiphonous filaments with adherent lower walls at the dichotomies (as in Dasyaceae, Heterocladieae, and some Lophothalia species), transversely divided pericentral cells, spermatangia covering cells of the filaments, and stichidia with whorls of 4–5 tetrasporangia are all distinctive features which point to a separate group or tribe for Wilsonaea.

References:

FALKENBERG, P. (1901). Die Rhodomelaceen des Golfes von Neapel und der angrenzenden Meeres-abschnitte. Fauna und Flora des Golfes von Neapel. Monogr. 26. (Friedländer: Berlin.)

KYLIN, H. (1956). Die Gattungen der Rhodophyceen. (Gleerups: Lund.)

SCHMITZ, F. (1893). Die gattung Lophothalia, J. Ag. Ber. Deutsch. Bot. Ges. 11, 212–232.

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

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.

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