Electronic Flora of South Australia Species Fact Sheet

Halophila decipiens Ostenfeld 1902: 260, with fig.

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

Selected citations: Aston 1973: 221. Beadle, Evans & Carolin 1972: 520. Green 1981: 6. den Hartog 1970: 254. Jacobs & Pickard 1981: 20. Sainty & Jacobs 1981: 236.

Synonym

H. baillonii sensu Holm 1885: 4, pls 1–3

Monoecious; stoloniferous perennial herb (Figs 10A, 11A,B), glabrous or with some unicellular hairs. Stolon about 1 mm in diameter. Roots 1 per node. Scales 3–5 mm long, obovate, keeled, glabrous or with scattered hairs on the outside particularly on the keel. Leaves (Fig. 11A,B) in pairs, delicate, bright green, glabrous or with scattered unicellular hairs on one or both faces, blade oblong-elliptical, rounded at the apex, 1–1.5 (–2.5) cm long, 2.5–4 (–6) mm broad, L/B usually 3–4; margin finely serrulate, crossveins 5–7 (–9) pairs. Petiole triquetrous, usually considerably shorter than the leaf blade. Squamules 1–2, linear, in the axil of the petiole. Spathes (Fig. 11A,C) enclosing one male and one female flower, borne on erect lateral shoots (3–) 5–7 (–10) mm long; spathal bracts 3–7 mm long, ovate, acuminate, glabrous or with scattered hairs on the oustide, keel usually finely serrulate. Male flower subsessile at first, with ovate tepals 1–1.5 mm long, pedicel 4–8 mm long at anthesis. Female flower solitary, sessile, hypanthium 1–2 mm long, tepals minute, styles 3. Fruit (Fig. 11A) ellipsoid, 3–5 mm long, at maturity splitting the spathe. Seeds about 30.

Type from the Gulf of Thailand, off Koh Kandat, on coral sand, 10 m deep (Schmidt 540, Feb. 1900); in C, L.

Selected specimens: Gipsy Point, Mallacoota Inlet, East Gippsland, Vic., 1.5–4 m deep (McConchie & Macauley, 10.xi.1980; MEL, 584594). Lee Point, Darwin, N.T., 0.5 m deep (Must 805, 6.x.1971; ADU, A41255). Punta Arenas, Mayaguez, Puerto Rico, dredged 15–20 m deep (Diaz-Piferrer, 31.viii.1963; ADU, A29123).


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

Distribution: A widespread pantropical species usually occurring only north of the Tropic of Capricorn. On the Western Australian coast it occurs south to Cockburn Sound and on the south-eastern Australian coast it occurs south to Mallacoota Inlet, Victoria.

Taxonomic notes: The population at Mallacoota Inlet has glabrous leaves (Fig. 11B,C). However, hairiness is a variable character in this species, and can vary considerably within a population and even on the same plant. The leaf margins are consistently serrulate.

References:

ASTON, H. (1973). Aquatic plants of Australia. (Melbourne University Press: Melbourne.)

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

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.)

HOLM, T. (1885). Recherche anatomiques et morphologiques sur deux monocotyledones submergées. (Halophila baillonii Asch. et Elodea densa Casp.). Bih. Kgl. Svenska Vetensk. Akad. Handl. 9(13), 1–18.

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. (1902). Hydrocharitaceae, Lemnaceae, Pontederiaceae, Potamogetonaceae, Gentianaceae (Limnanthemum), Nymphaceae. Bot. Tidsskr. 24, 260–263.

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

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 10A, 11A-C.

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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