Cynanchum pedunculatum R.Br.

Apocynaceae

Brown, R. (1810) Memoirs of the Wernerian Natural History Society, Edinburgh 1 : 45. Type: Northern Territory, Arnhem North Bay [Melville Bay], 14 FEb. 1803, R. Brown; lecto: BM. Fide P. I. Forster, Austrobaileya 3: 461 (1991).

A slender vine not exceeding a stem diameter of 2 cm.

Leaf blades about 3.5-7 x 2.5-5 cm, petioles about 2.5-4.5 cm long. Upper and lower leaf blade surfaces clothed in short pale-coloured hairs. Lateral veins about 4-6 on each side of the midrib. Twigs, stems and petioles clothed in short pale-coloured hairs. A group of about 5 reddish colleters (small finger-like glands) usually visible on the upper surface of the midrib near its junction with the petiole. A pair of reduced leaves often present in the axil of one leaf of each pair, usually associated with a flower or fruit peduncle. All plant parts produce a copious milky exudate.

Inflorescence umbelliform, a condensed raceme, about 8 cm long, each flower subtended by a bract about 2.5-4 mm long. Flowers about 5-6 mm diam., scarcely opening. Sepals reflexed, about 3-3.5 mm long, glands present on the inner surface close to the base. Corolla tube about 1-2 mm long, lobes about 3-4 mm long. Corona resembles a ruffled skirt around the staminal column at the base of the corolla tube. Anthers about 1.25-2 mm long, including the terminal appendage. Pollen aggregated in pollinia. Carpels two, each about 2.5 mm long. Ovules numerous.

Fruits often paired. Individual fruiting carpels about 5.5-9 x 2.5-3.5 cm. Seeds numerous. Seeds about 6-13 x 3-8 mm. Plumes about 20 mm long. Embryo about 5 mm long. Cotyledons about 3-3.5 x 2 mm. Radicle about 1.5 mm long.

Cotyledons oblong to elliptic, mainly glabrous, about 19-21 x 9-12 mm. First pair of leaves ovate-triangular, apex acute, base truncate to obtuse. Third and fourth leaves cordate. At the tenth leaf stage: all plant parts produce a copious white exudate when cut or broken. Leaf blade narrowly cordate, apex acute, base auriculate. Stipules gland-like, about 0.2 mm long. Usually 2-4 small reddish colleters (glands) present on the upper surface of the midrib close to its junction with the petiole. All plant parts densely clothed in short, curved pale-coloured (whitish) hairs. Midrib +/- flush with the upper surface. Seed germination time 14 days.

Endemic to Australia, occurs in WA, NT, CYP, NEQ and CEQ. Altitudinal range from near sea level to 750 m. Grows in open forest and vine thicket.

Plants die back to the perennial rootstock during the dry season and shoot following the onset of the pre-wet season storms. Forster (1996).

Cynoctonum pedunculatum (R.Br.) Decne., Candolle Prodromus 8: 529(1844). Vincetoxicum pedunculatum (R.Br.) Kuntze, Revis. Gen. Pl. 2: 424(1891). Cynanchum brownianum Schult., Systema Vegetabilium 6 : 97(1820). Cynoctonum erubescens (R.Br.) Decne., Candolle Prodromus 8: 529(1844). Vincetoxicum erubescens (R.Br.) Kuntze, Revis. Gen. Pl. 2: 424(1891). Cynanchum erubescens R.Br., Memoirs of the Wernerian Natural History Society, Edinburgh 1 : 45(1810), Type: Queensland, Endeavour River, 1770, Banks & Solander; lecto: BM. Fide P. I. Forster Austrobaileya #: 461 (1991).