Hypserpa decumbens (R.Br. ex Benth.) Diels

Diels, F.L.E. (1910) Das Pflanzenreich Heft 46: 212.

Hyperpa; Hairy Hypserpa

Vine stem diameters to 14 cm recorded. Concentric growth rings visible in stem transverse sections.

Leaf blades about 4.5-13 x 2.5-7.5 cm, petioles about 1-2.2 cm long. Young twigs and petioles densely clothed in dark brown or pale hairs. Upper surface of the leaf blade eventually becoming almost glabrous. Underside of the leaf blade clothed in brown or pale hairs. Oak grain in the twigs.

Male flowers: Flowers borne in short dense racemes. Sepals four or five, ovate, about 1-2 mm long, outer surface clothed in hairs. Petals five or six, arranged in two whorls. Petals obovate or spathulate, about 2-3.5 x 1 mm. Stamens 12-15, each about 2-3 mm long. Anthers globose or wider than long. Female flowers: Flowers borne in short racemes. Sepals two to four, triangular, about 1-2 mm long. Petals six to eight, outer petals oblong, about 2-2.5 mm long, inner petals obovate or spathulate, about 1.5 mm long. Ovaries three. Ovules one per ovary.

Fruits +/- globose, sometimes paired, about 6-7 mm diam. Seeds about 5 x 3.5 mm. Embryo circular or U-shaped, about 11-12 mm in total length. Cotyledons up to 6 mm long. Radicle about 3-6 mm long. Radicle and cotyledons of similar widths.

Cotyledons linear, about 10-15 x 1 mm, no midrib or other venation visible. First pair of leaves ovate, apex apiculate, base rounded. At the tenth leaf stage: leaf blade cordate, about 8 x 5 cm, apex apiculate, base cordate, midrib slightly raised on the upper surface. Seed germination time 81 days.

Endemic to Australia, occurs in NT, CYP, NEQ, CEQ and southwards as far as north-eastern New South Wales. Altitudinal range in northern Australia from near sea level to 1150 m. Grows in lowland an upland rain forest.