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Electronic Flora of South Australia Species Fact Sheet

Ulva lactuca Linnaeus.

Phylum Chlorophyta – Order Ulvales – Family Ulvaceae

Selected citations: Sliding 1968: 540, figs 1–5. Koeman & van den Hoek 1981: 31, figs 53–77. Papenfuss 1960: 303, figs 1–3, 10. Womersley 1956: 353 (in part only).

Thallus (Fig. 44A) grass-green, usually with a single frond from the holdfast, entire or irregularly lobed or divided, to 15 cm long and 1–10 cm across; margin entire, surface smooth. Cells in surface view (Fig 45A- C) in short rows becoming more irregular below, isodiametric to slightly elongate, (10–) 12–18 (–20) µm across or long above, 20–25 pm long below; pyrenoids 1–2 (–3) per cell. Thallus 40–60 µm thick in upper parts (Fig. 45A) with cells in sectional view rather square to rectangular, L/B 1.0–1.4 and 18–22 µm long; 60–85 µm thick in mid and lower parts (Fig. 45B) with cells in section L/B 1–1.2 (–1.4) and 22–26 µm long, becoming 75–100 (–250) µm thick near the base with a narrow to moderately broad central mass of rhizoids (Fig. 45C).

Reproduction: Reproduction (Bliding 1968, p. 542). Generations isomorphic, the sporophyte producing quadriflagellate zoo(meio)spores, and the gametophytes unisexual with biflagellate anisogametes which can germinate directly to form the gametophyte again.

Type from the west coast of Sweden; in LINN.

Selected specimens: Christies Beach, S. Aust., 6 m deep near sewer outfall (Clarke & Engler, 10.xi.1980 and 11.iii.198 I; ADU, A51838 and A52029 respectively). Hobsons Bay, Port Phillip, Vic., 0–0.5 m deep at Power Station outfall (Watson, 1.v.1972; ADU, A42338).

Distribution map based
on current data relating to
specimens held in the
State Herbarium of SA

Distribution: Recorded from most oceans; in Europe U. lactuca is a cold temperate to Arctic species, and records from warmer seas need verification.

In southern Australia, known from Christies Beach and St Kilda, S. Aust. and Port Phillip, Vic. and recorded from other scattered localities most of which require verification.

Taxonomic notes: U. lactuca appears to be far less common around southern Australia than U australis, U. rigida and U. taeniata. It is characterised by a single, simple to irregularly divided and relatively thin thallus with an entire margin, and cells which in cross section are almost square (rarely with a length more than 1.5 times their breadth), fairly tightly packed and with rounded corners. These features agree well with Bliding's and Papenfuss' descriptions, although Australian material more frequently has 2 (–3) pyrenoids per cell compared to the one in plants from Sweden.


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

KOEMAN, R.P.T. & VAN DEN HOEK, C. (1981). The taxonomy of Ulva (Chlorophyceae) in the Netherlands. Br. phycol. J. 16, 9–53.

PAPENFUSS, G.F. (1960). On the genera of the Ulvales and the status of the order. J. Linn. Soc. Bot. 56, 303–318, Plates 1–6.

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

Illustrations in Womersley Part I, 1984: FIGS 44A, 45 A–C.

Figure 44 image

Figure 44   enlarge

Fig. 44. A. Ulva lactuca (ADU, A42338). B. Ulva australis, on Amphibolis (ADU, A51817). C. Ulva australis (ADU, A51819). D. Ulva rigida (ADU, A51821).

Figure 45 image

Figure 45   enlarge

Fig. 45. A–C. Ulva lactuca (ADU, A52029). A. Surface and cross section views of young thallus. B. Ditto, of mid thallus. C. Ditto, rhizoidal region near base. D–F. Ulva australis (ADU, A51819). D. Surface and cross section views of young thallus. E. Ditto, of mid thallus. F. Cross section view of rhizoidal region near base. G–J. Ulva rigida (ADU, A51816). G. Thallus margin with spines. H. Cross section view of young thallus. I. Surface and cross section views of mid thallus. J. Surface view of rhizoidal region near base.

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