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Electronic Flora of South Australia Genus Fact Sheet

Genus TYLOTUS J. Agardh 1876: 428

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Dicranemataceae

Thallus decumbent, complanately and irregularly subdichotomously branched, with the basal few centimetres attached by haptera from the lower surface, branches flat, 5–12 mm broad, margins smooth, linear to sinuous, unthickened, epilithic. Structure multiaxial, with a broad inner cortex of large ovoid cells (without any differentiated medulla) and an outer cortex of small cells; inner cells with abundant secondary pit-connections.

Reproduction: Sexual thalli monoecious with female on lower and male structures on upper sides of blades; procarpic. Carpogonial branches 3-celled, scattered, laterally attached to outer cortical cells but outwardly directed, with the adjacent cortical cells developing anticlinal filaments. Supporting cell acting as auxiliary cell, developing a fusion cell which initiates lateral gonimoblast filaments forming a hemispherical placenta at the base of the cystocarp chamber; upper surface of carposporophyte becoming undulate with parallel gonimoblast filaments cutting off single, terminal, relatively small carposporangia. Pericarp thick, ostiolate. Spermatangia in small, sunken clusters on upper surface of fronds.

Tetrasporangia in nemathecia on upper surface, zonately divided.

Life history triphasic with isomorphic gametophytes and tetrasporophytes.

Type species: T. obtusatus (Sonder) J. Agardh 1876: 428.

Taxonomic notes: Tylotus, a genus with one Australian and one Japanese species, was studied in detail by Kraft (1977b, p. 245).


AGARDH, J.G. (1876). Species Genera et Ordines Algarum. Vol. 3, Part 1 - Epicrisis systematis Floridearum, pp. i-vii, 1–724. (Weigel: Leipzig.)

KRAFT, G.T. (1977b). Studies of marine algae in the lesser-known families of the Gigartinales (Rhodophyta). H. The Dicranemaceae. Aust. J. Bot. 25, 219–267.

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

Author: G. T. Kraft & 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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