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Electronic Flora of South Australia
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Electronic Flora of South Australia Genus Fact Sheet

Genus ULVA Linnaeus 1753: 1163, nom. cons.

Phylum Chlorophyta – Order Ulvales – Family Ulvaceae

Thallus flat, simple or laciniate, or much branched with elongate, plane or ruffled branches, attached by a small holdfast formed by rhizoidal extensions from the lower cells which then increase in size. Blade formed of two layers of cells adherent throughout (except in germination stages less than a few mm high). Cells with a single chloroplast occupying normally the outer part of the cell, with 1 to 4 pyrenoids.

Reproduction: Usually anisogamous but unrecorded for species in Australia.

Life history. Most species diplohaplontic with isomorphic generations.

Type species: Ulva lactuca Linnaeus.

Taxonomic notes: Ulva is a common, cosmopolitan genus, usually occurring in the lower eulittoral zone and the uppermost sublittoral. Previously, the Australian taxa (apart from U. spathulata) had been lumped into U. lactuca L. (see Womersley 1956, p. 353), but six species can be distinguished on southern Australian coasts, and U. lactuca appears to be one of the less common species. Probably other species than those discussed below occur on southern Australian coasts, especially on the south-west coasts of Western Australia.

The following treatment is based entirely on habit and structure of the thallus, following the criteria used by Bliding (1968). However, it is highly desirable that these taxonomic hypotheses should be tested by cultural and experimental crossing studies.


BLIDING, C. (1968). A critical survey of European taxa in Ulvales, II. Ulva, Ulvaria. Monostroma, Kornmannia. Bot. Notiser 121, 535–629.

LINNAEUS, C. (1753). Species Plantarum. Vols 1, 2. (Laurenti Salvii: Stockholm.)

WOMERSLEY, H.B.S. (1956). A critical survey of the marine algae of southern Australia. I. Chlorophyta. Aust. J. mar. freshw. Res. 7, 343–383.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (31 May, 1984)
The Marine Benthic Flora of Southern Australia
Part I
©Board of the Botanic Gardens and State Herbarium, Government of South Australia


1. Thallus (0.5–) 1–3 times as long as broad, not divided into long branches from near the base


1. Thallus unbranched or divided from near the base, with long and relatively narrow (L/B 6–20), plane, ruffled or spathulate-ended branches


2. Thallus usually with a single frond from the holdfast; cells in transection of thallus usually L/B <1.5 throughout

I U. lactuca

2. Thallus with a single or several fronds from the holdfast or just above; cells in transection of mid and lower parts of the thallus mostly L/B 1.5–3


3. Thallus usually with several fronds from near the base, without marginal spines; cells in transection of mid and lower parts of thallus L/B (1–) 1.5–2, more or less parallel sided with rounded corners but not tapering outwardly

U. australis

3. Thallus simple or branched near the base, usually with microscopic spines on areas of intact margin; cells in transection of upper parts of thallus rounded, in mid and lower parts elongate (L/B 2–3 (–5)) and tapering outwardly (to the thallus surface)

U. rigida

4. Thallus to 10 cm high, branches narrow (1–4 mm) for half or more of their length, expanding above to lobes 0.5–2 cm broad. 4

U. spathulata

4. Thallus over 10 cm high, simple or branched, branches broadest (over 1 cm) in their lower half and tapering gradually above and near their bases, margins either more or less plane or strongly ruffled


5. Thallus much divided near the base, branches lanceolate, relatively flat, margins largely entire and without microscopic spines, central region of branches often paler forming a vague midrib (in dried specimens)

U. fasciata

5. Thallus simple or occasionally branched, margins usually moderately to strongly ruffled throughout, usually with marginal microscopic spines.

U. taeniata

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