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Dichapetalum australianum C.T.White
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Contributions to the Queensland Flora, No. 7. Proceedings of the Royal Society of Queensland 53: 211-212 (1942).

Type citation: "Cook District. – Slopes of Mt. Fraser, alt. 2,000 ft., in rain-forest gully, L.J. Brass, No. 2510 (fruits), 16th April, 1932..." Type: Australia. Cook District. Slopes of Mt Fraser, alt. 2000 ft, rain forest gully, 16 Apr 1942, L.J.Brass 2510 (hlo: BRI AQ0419158).

[Dichapetalum papuanum auct. non (Becc.) Boerl.: Hewson (1984: 218); Hyland et al. (1994: 303; 1999; 2003); Cooper & Cooper (2004)]

Illustrations: (all as D. papuanum) Hewson (1984: 216); Cooper & Cooper (1994: 91); Cooper & Cooper (2004: 150); Zich et al. (2020).

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Figure 3. Dichapetalum australianum: A. 3- and 4-flowered female inflorescences (not vouchered) B. Petiole showing short taper onto abaxial primary vein as well as glands on leaf blade (Cooper 2934 [CNS]; C. Ripe fruit dehisced and indehisced, as well as cross-section, arillate seeds and a naked seed (Cooper 123 [CNS]). Photos: A. G. Sankowsky; B. W.E. Cooper; C. Artwork W.T.Cooper.

Dioecious, slender and sapling-like to c. 4 m then becoming a vine to the canopy; stem diameter to 30 mm; bark reddish-brown with numerous circular or horizontal lenticels; some branches back-arching; twigs lenticellate, sparsely sericeous on new growth becoming glabrous; indumentum white; stipules caducous, triangular, sericeous, c. 3 mm long; petioles thickened, arched and sub-peltate (not always distinct on dried specimens), 3–7 mm long not including taper; taper along midrib extending for 2–3 mm and acuminate at junction with primary vein, wrinkled, sparsely sericeous becoming glabrous, dark brown. Leaves elliptic, obovate or rarely lanceolate, 40–170 mm long and 15–66 mm wide, coriaceous; new growth sericeous; abaxial surface glossy, with sparse appressed hairs at base and along midrib becoming sparser, glands 0–6 (rarely 8) near base and sometimes a few scattered in mid to distal sections; adaxially sparsely sericeous on midrib and a few solitary white hairs along margin especially at indentations, becoming glabrous, glands scattered; coriaceous; discolorous; base often slightly asymmetrical, attenuate or rarely cuneate; apex shortly acuminate and the ultimate tip narrowly rounded, caudate or acute; margin shallowly repand; venation camptodromous proximally and brochidodromous distally; primary vein distinctly raised on both surfaces or flush and raised within a groove; secondary veins 4–8 pairs, proximal veins at c. 40º to the midrib and distal veins at 10–30º to the midrib, slightly raised on both surfaces; tertiary venation reticulate, densely pitted within each reticulation on abaxial surface. Gynoecious inflorescence an axillary raceme or shortly peduncled fascicle, 1–3 (4)-flowered; bracts at base of peduncle ovate, c. 0.3 mm long, sparsely sericeous; peduncles 3.5–6 mm long, sparsely sericeous; pedicels articulate, 0.6–0.8 mm long, thinly pilose; bracts 1 or 2 along pedicel, triangular, c. 1 mm long, sericeous; flower fragrance not detected, diameter c. 3.5 mm, c. 3 mm long; calyx tubular at base, c. 3.2 mm long; sepals 5, ovate, c. 1.8 mm long; abaxially sparsely sericeous, outer pair more densely pubescent especially along margins, adaxially pubescent, orange; petals 5, ovate, slightly longer than sepals, c. 2 mm long, glabrous or a few sparse hairs abaxially, adaxially glabrous or with 1 or a few hairs, white or lemon, apex emarginate to c. 0.25 mm; stamens 5; filaments narrowly triangular, c. 1 mm long; anthers introrse; staminodes 5, bilobed-globose, c. 0.25 long and 0.5 wide, glabrous, orange; ovary ovoid, 2- or 3-locular, c. 1 x 1 mm, pubescent; stigma sessile, 3-lobed, diameter c. 0.3 mm. Staminate inflorescence axillary or ramiflorous, 6–10-flowered, repeatedly dichotomously branched cyme, often in pairs; bracts clustered at base, ovate, c. 1 mm long, sparsely sericeous; peduncle 3.5–7 mm long, sparsely sericeous; pedicel 0.8–1.5 mm long, sparsely sericeous, bracts absent; flower fragrance not detected, diameter c. 2.5 mm and c. 2.5 mm long; calyx tubular at base; sepals 5, ovate, 1–1.25 mm long, abaxially sparsely sericeous through mid-section and tomentose near margins, adaxially tomentose, orange at base and lemon towards apex; petals 5, obovate or elliptical, cucullate, minutely emarginate, c. 1 mm long and 0.5 mm wide, glabrous or with a few crisped hairs on lower abaxial surface, lemon or whitish; stamens 5, filaments slender-triangular with a few pale hairs below the centre, c. 1.5 mm long, anthers introrse; staminodes 5, laterally compressed and oblate, glabrous; pistillode pubescent. Fruit pedicel 1–2 mm long, sparsely sericeous; capsule 1–3-lobed, oblate, 7–20 x 10–24 mm, surface slightly dimpled with a few sparse appressed white hairs visible with a lens mostly towards base, orange; seeds 1–3, reniform, straw-coloured, c. 12 mm long and 7 mm wide, with red arils completely enclosing the seeds. Fig. 1 & 3

Specimens examined: Queensland. Cook District: Vine Creek area, off Tully Falls Road, March 2006, Ford 4796 (CNS); Djallon Creek Scenic Drive, Palmerston National Park, Nov 2008, Forster PIF17935 & Spokes (CNS); Pugh Creek, Mirriwinni, Jan 1988, Jago 663 (CNS); Weinert Creek, Babinda, Nov 2013, RL Jago 556 (CNS); Westcott Road, Topaz, Jan 1992, Cooper & Cooper 123 (CNS); Westcott Road, Topaz, Oct 2022, Cooper 2934 (CNS); Timber Reserve 1230, Boonjee Logging Area, Nov 1976, Hyland 9164 (CNS); Wooroonooran National Park, Bartle Frere track before Bobbin Falls, Oct 1997, Forster PIF21755, Jensen & Booth (BRI); Lake Barrine, Nov 2013, Gray 9619 (CNS); SFR 191, Parish of Barron, Oct 1991, Hyland 14253 (CNS); SF 191 Wongabel, Feb 1996, Forster PIF 18628 (CNS); Scenic Reserve 440, Lake Euramoo, Dec 1971, Hyland 5738 (CNS); Tolga Scrub, Nov 1999, Gray 7701 (CNS); Haren Creek, 3.5 km SW of Kuranda, March 1998, Wannan BSW687 & RL Jago (BRI & NSW); 4.5 km from Whyanbeel Road on track to Stewart Creek 13.7 km NW of Mossman, Nov 1988, Jessup, Guymer & McDonald GJM425 (BRI); Coral Sea Drive southwest of Mossman, Dec 2002, Jago 6353 (BRI); Baileys Creek, N of Daintree River, Jan 1962, Webb & Tracey 6508 (BRI); Near Wetherby Homestead in NW foothills of Mt Danbullan Range, 6 km NW of Mt Molloy, June 1984, Moriarty 2921 (CNS); Hunter Creek, Brooklyn, Dec 2011, Sankowsky 4178A & Sankowsky (BRI); Isabella McIvor Road, 3 km, June 1992, Le Cussan 111 (CNS).

Figure 3. Dichapetalum australianum: A. 3- and 4-flowered female inflorescences (not vouchered) B. Petiole showing short taper onto abaxial primary vein as well as glands on leaf blade (Cooper 2934 [CNS]; C. Ripe fruit dehisced and indehisced, as well as cross-section, arillate seeds and a naked seed (Cooper 123 [CNS]). Photos: A. G. Sankowsky; B. W.E. Cooper; C. Artwork W.T.Cooper.

Diagnostic features. Dichapetalum australianum is distinct by being dioecious; petiole taper along midrib extending for 2–3 mm and acuminate at junction with primary vein; hermaphrodite inflorescence 1–3(4)-flowered, sparsely sericeous; staminodes gabrous; fruit an oblate orange capsule, usually with 3 seeds enclosed by copious red aril. D. australianum differs from D. papuanum by flower length (2.5–3 mm v. 1–2 mm); disk lobes (glabrous v. tomentose); fruit (oblate and dehiscent v. obovate and indehiscent).

Phenology. Flowers have been recorded from September to February and fruit from December to June.

Distribution & habitat. Dichapetalum australianum is restricted to complex notophyll and mesophyll vine forest as well as riparian forest almost entirely within the Wet Tropics Bioregion from the Tully River area north, and extending to Isabella Falls near Cooktown in the Cape York Bioregion, at altitudes between sea level and 1130 m. It co-occurs with Aglaia australiensis Pannell, Aglaia meridionalis Pannell, Aglaia monticola W.E.Cooper & P.I.Forst. Argyrodendron peralatum (F.M.Bailey) Edlin ex Boas, Beilschmiedia recurva B.Hyland, Beilschmiedia tooram (F.M.Bailey) B.Hyland, Castanospora alphandii (F.Muell.) F.Muell., Cnesmocarpon dasyantha (Radlk.) Adema, Cryptocarya mackinnoniana F.Muell., Cryptocarya onoprienkoana B.Hyland, Doryphora aromatica (F.M.Bailey) L.S.Sm., Elaeocarpus grandis F.Muell., Endiandra monothyra B.Hyland, Firmiana papuana Mildbr., Flindersia brayleyana F.Muell., Franciscodendron laurifolium (F.Muell.) B.Hyland & Steenis, Myristica globosa subsp. muelleri (Warb.) W.J.de Wilde, Prunus turneriana (F.M.Bailey) Kalkman, Syzygium endophloium B.Hyland, Syzygium gustavioides (F.M.Bailey) B.Hyland, Syzygium papyraceum B.Hyland and Toechima monticola S.T.Reynolds.

Conservation status. Based on known localities, the Extent of Occurrence (EOO) of Dichapetalum australianum is estimated to be 8,800 km|^2^| and Area of Occupancy (AOO) is 184 km|^2^| (calculated with GeoCat; Bachman et al. 2011). The species is represented in conservation reserves and there are no immediate threats evident. As such, D. australianum would be categorised as being of Least Concern.

Etymology. The species epithet is from the Latin australis meaning southern.

Notes. Dichapetalum australianum was first described in 1942 from a specimen collected at Mt Fraser, near Julatten, by L.J. Brass. Leenhouts (1956 and 1957) revised the genus Dichapetalum for Asia, Australia and Melanesia and included D. australianum within the concept of D. papuanum. He suggested that D. papuanum is best characterised by its obovate nearly glabrous fruit and that fruiting material is desirable to settle status. The fruit were described and illustrated as obovate and indehiscent which differs markedly from what is observed for D. australianum. The Type specimen for D. papuanum (Beccari PP307 L) was collected from Ramoi (near Sorong in West Papua, Indonesia), although it has been incorrectly annotated as being from Papua New Guinea. D. papuanum subsp. borneense Leenh. occurs on Sabah (Malaysian Borneo) (Haviland 2192 K).