Electronic Flora of South Australia Species Fact Sheet

Halophila ovalis (R. Brown) J.D. Hooker 1858: 45.

Phylum Magnoliophyta – Subphylum Seagrasses – Class Liliopsida – Subclass Alismatidae – Order Hydrocharitales – Family Hydrocharitaceae

Selected citations: Beadle, Evans & Carolin 1972: 519. Blackall & Grieve 1954: 10. Green 1981: 6. den Hartog 1970: 240, fig. 62. Jacobs & Pickard 1981: 20. Ostenfeld 1916: 38. Sainty & Jacobs 1981: 236, with fig. Willis 1970: 77 (in part).

Synonym

Caulinia ovalis R. Brown 1810: 339.

Dioecious; annual or perennial glabrous herbs (Figs 10B,C, 11D,E); with much-branched stolons forming extensive beds. Stolons 1–2 mm in diameter. Roots usually 1 at each node. Scales hyaline, (2–) 3–5 mm long, suborbicular to obovate, notched at the summit. Leaves in pairs, glabrous, usually oblong to obovate with a rounded apex and base, 1–3 (–4) cm long, 0.5–2 cm wide, L/B 2–3 [but considerable variation can occur even in one population (Fig. 11F,G)]; margin entire; crossveins (7–) 10–12 (–19) pairs, arising at angles of 45–60°, some crossveins forked. Petiole terete. Squamules 2, lanceolate in axil of petiole. Spathes enclosing either a male or a female flower, sessile on the prostrate stolon; spathal bracts 5–8(40) mm long, lanceolate, keeled. Male flower (Fig. 11E) at first subsessile, pedicel up to 2.5 cm long at anthesis; tepals 3–4 (–6) mm long, membranous with a prominent central vein, hooded, imbricate; pollen grains ellipsoid. Female flower (Figs 10B, 11 D) solitary, sessile on a horizontal stolon with hyaline scales at each node. Ovary ovoid, 1.5–2 mm long, hypanthium 3–5 (–8) mm long; tepals up to 1 mm long; styles 3, 10–25 (–40) mm long. Fruit ovoid to globose, 3–5 mm long, with a persistent hypanthium. Seeds 20–30, subglobose.

Type from Queensland, Australia (exact locality unknown) (R. Brown 5816); in BM.

Selected specimens: Whitfords Beach, Perth, W. Aust., 5 m deep on sand (Lipkin, 2.ii.1982; ADU, A52975). Freshwater Bay, Swan River estuary, W. Aust., 1.5 m deep (Hillman, 21.iv.1982; UWA, 3163 and ADU, A53177). Point Walter, Swan River estuary, W. Aust. (Allender, 28.i.1969; UWA, A1208 and A1209). Cowaramup Bay, W. Aust., 2–3 m deep (Clarke & Engler, 1.ix.1979; ADU, A50666). Shelley Beach, Pallarenda, Queensland (Birch, 22.viii.1978; ADU, A52972). Tetel I., Florida Is, Solomon Is, in pools on reef (Bailey 91, 9.vii.1965; ADU, A53388).


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

Distribution: Widely distributed in tropical and warm temperate waters of the Indo-Pacific region and extending down the Western Australian coast as far as Cowaramup Bay and down the eastern Australian coast to about the Victorian border (Jacobs & Pickard 1981, p. 20).

Taxonomic notes: In the absence of fertile material, H. ovalis may usually be distinguished by the leaves which are generally more ovate-oblong with a rounded apex and frequently more rounded at the base than H. australis. However, as discussed earlier, the species exhibits great morphological variation in leaf size, leaf shape, L/B ratio and also the ratio of leaf blade to petiole length. A determination cannot be made with a single leaf but needs to take into account the whole population.

References:

BEADLE, N.C.W., EVANS, O.D. & CAROLIN, R.C. (1972). Flora of the Sydney region. 2nd edn. (Reed: Sydney.)

BLACKALL, W.E. & GRIEVE, B.J. (1954). How to know Western Australian Wildflowers. Part I. (University of Western Australia Press: Perth.)

BROWN, R. (1810). Prodromus Florae Novae Hollandiae et Insulae Van-Diemen. (Taylor: London.)

DEN HARTOG, C. (1970). The seagrasses of the World. Verh. k. ned. Akad. Wet. Afd. Natuurk., ser. 2, 59(1), 1–275 (-1–31 Plates).

GREEN, J.W. (1981). Census of the Vascular Plants of Western Australia. (Western Australian Herbarium: South Perth.)

HOOKER, J.D. (1858). The Botany of the Antarctic voyage of H.M. Discovery Ships Erebus and Terror, in the years 1839–1843. III. Flora Tasmaniae. Vol. 2. (Monocotyledones). (Reeve: London.)

JACOBS, S.W.L. & PICKARD, L. (1981). Plants of New South Wales. A census of the Cycads, Conifers and Angiosperms. (National Herbarium of New South Wales: Sydney.)

OSTENFELD, C.H. (1916). Contributions to West Australian Botany. I. The Seagrasses of West Australia. Dansk. bot. Arkiv. 2(6), 1–44.

SAINTY, G.R. & JACOBS, S.W.L. (1981). Water Plants of New South Wales. (Water Resources Commission of New South Wales: Sydney.)

WILLIS, J.H. (1970). A handbook to plants in Victoria. Vol. 1. 2nd edn. (Melbourne University Press: Melbourne.)

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 10B,C, 11 D–G.

Figure 10 image

Figure 10   enlarge

Fig. 10. A. Halophila decipiens (MEL, 584594). Habit, showing female flower with 3 stigmas. B,C. Halophila ovalis. B. Habit, female plant showing flower with 3 stigmas (ADU, A53177 from Western Australia). C. Habit, small leaved plant (ADU, A52972 from Queensland).

Figure 11 image

Figure 11   enlarge

Fig. 11. A–C. Halophila decipiens. A. Habit of fertile plant with hairy leaves from Northern Territory. B. Portion of fertile plant with glabrous leaves from Mallacoota Inlet, Victoria. C. Portion of branch, with leaves removed, showing young male and female flowers. (A from ADU, A41255. B,C from MEL, 584594.) D–G. Halophila ovalis. D. Habit of female plant. E Portion of stolon showing male flower on elongated pedicel. F. Variation in leaf shape on a plant from Queensland. G. Variation in leaf shape on a plant from Western Australia. (D,E,G from ADU, A52975. F from ADU, A52972.)


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