Lophopetalum arnhemicum Byrnes

Byrnes, N.B. (1971) Journal and Proceedings of the Royal Society of New South Wales 96: 85. Type: Katherine Gorge National Park, N.Byrnes 921; 7 Sep. 1968 (Darwin 2852). Isotypes: K, L, A, CANB, NSW, BRI, PERTH, MEL, NT.

Dead bark orange when cut or a mustard coloured layer visible under the dead bark.

Midrib slightly raised on the upper surface. Leaf blades about 6-17 x 1.5-3.5 cm. Lateral veins forming indistinct loops inside the blade margin. Stipules small and inconspicuous. Petioles and smaller twigs reddish.

Calyx lobes short and broad, rounded at the apex. Petals about 3.5 x 3.5 mm. Disk fleshy, nearly flat. Stamens inserted on the disk. Ovary immersed in the disk. Ovules about 6-8 per locule.

Capsules about 6-8 cm long. Seeds with a marginal wing, seed + wing about 35 x 10 mm.

Seed germination time 13 to 18 days. Cotyledons usually remaining within the seed coat. First pair of leaves with the midrib raised on the upper surface. At the tenth leaf stage: leaf blade narrowly lanceolate, lateral veins forming loops inside the blade margin; midrib raised on the upper surface; stipules filiform, small and inconspicuous, visible with a lens.

Endemic to Australia, occurs in NT on the Katherine, South Alligator and East Alligator River catchments. Altitudinal range from near sea level to about 300 m. (May also occur in CYP but better material is needed.) Usually a rheophyte growing along watercourses in sandstone.