Electronic Flora of South Australia Family Fact Sheet


Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae

Thallus dichotomously or becoming laterally branched by unequal development, branches compressed to flat, with a small-celled, densely phaeoplastic cortex 1–5 cells thick and a large-celled, not or sparsely phaeoplastic medulla 1–4 (–7) cells thick. Growth from a single, transversely orientated apical cell. usually slightly protruding at the apex.

Reproduction: Reproduction with the sporophyte producing tetrahedrally divided tetrasporangia and by separate female and male plants with oogonial and antheridial sori.

Taxonomic notes: The Dictyoteae is a well defined tribe of four genera, all present in southern Australia. The differences between the genera are useful ones which are satisfactory for most species, but some plants and a few species from elsewhere [e.g. Pachydictyon aegerrime Allender & Kraft (1983, p. 116) from Lord Howe Island, which has a cortex two cells thick only at the thallus margins] "only just" qualify in their particular genus.


ALLENDER, B.M. & KRAFT, G.T. (1983). The marine algae of Lord Howe Island (New South Wales): The Dictyotales and Cutleriales (Phaeophyta). Brunonia 6, 73–130.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
Part II
©Board of the Botanic Gardens and State Herbarium, Government of South Australia


1. Surface of thallus with or without proliferations or surface ramelli; transverse section with a single cortical layer and a single medullary layer (rarely either layer is 2 cells thick near the base of occasional Glossophora plants)


1. Surface of thallus without proliferations (except rarely, following damage, or in Dilophus marginatus); transverse section at least marginally with either more than one medullary layer, or on old parts, more than one cortical layer around the branch


2. Thallus without surface proliferations or ramelli, except occasionally from near the base or margins; usually less than 1.5 cm broad, regularly branched


2. Thallus surface usually densely covered with ramelli 1–3 mm long; thallus usually 1–5 cm broad, sparingly subdichotomously branched


3. Thallus 2–4 medullary cells thick at least marginally, cortex single layered


3. Thallus with a single layer of medullary cells and a cortex 2–5 cells thick around on older, lower branches


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