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Leavs and flowers. Copyright CSIRO

Leaves and fruit. Copyright CSIRO

Leaves and fruit. Copyright CSIRO

Scale bar 10mm. Copyright CSIRO

10th leaf stage. Copyright CSIRO

Cotyledon stage, epigeal germination. Copyright CSIRO

Heterostemma acuminatum

Family

Apocynaceae

Scientific Name

Heterostemma acuminatum Decne.

Decaisne, J. (1838) Ann. Sci. Nat. Bot. ser. 2 9: 268. Type: Java, Leschenault s.n.; holo: P.

Stem

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

Leaves

Twigs slightly flattened, i.e. laterally compressed. Twigs and petioles produce a clear or milky exudate. Leaf blades about 7.5-16 x 4-13 cm, petioles about 3.5-6 cm long. A line of small 'glandular stipules' present on the twigs between the points of attachment of the petioles of each pair of leaves. Several (about 10) colleters (small finger-like glands) present on the upper surface of the midrib near its junction with the petiole.

Flowers

Inflorescence a panicle of compound racemes or umbels. Flowers about 10-12 mm diam. Sepals about 2 mm long, margins fimbriate. Corolla tube about 3 mm long (more disk-like than tubular), lobes about 4 mm long, glabrous. Staminal corona ornate, star-shaped, 5-lobed, each lobe about 1.1 x 1 mm, spur-like, alternating with the corolla lobes. Pollen aggregated in pollinia. Carpels about 1.5 mm long. Ovules numerous.

Fruit

Fruiting carpels usually paired. Individual fruiting carpels about 10-13 x 0.5-0.6 cm. Seeds numerous, each seed about 13-15 x 7 mm, curled around an imaginary longitudinal axis. Plumes silky, white, about 20-40 mm long attached to the end of the seed. Embryo about 11-12 mm long, cotyledons about 8 mm long, radicle about 3 mm long.

Seedlings

Cotyledons elliptic, about 20-28 x 10-14 mm, 3-veined at the base. First leaves ovate, apex acuminate, base obtuse, upper and lower leaf surfaces clothed in hairs. At the tenth leaf stage: leaf blade ovate, apex acuminate, base cordate. Upper and lower leaf blade surfaces clothed in minute hairs at least when young. Midrib depressed on the upper surface, lateral veins about 4-5 on each side. Colleters about 5. Stipule-like glands about 0.5 mm long present on the stem between the points of attachment of the petioles. Stems twining. Petioles and stems clothed in pale brown hairs. Seed germination time 57 days.

Distribution and Ecology

Occurs in CYP, NEQ, CEQ and further south in Queensland. Altitudinal range from near sea level to 680 m. Grows in vine thicket, monsoon forest and open areas in rain forest. Also occurs in New Guinea and other parts of Malesia.

Natural History & Notes

Slender Vine

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Synonyms

Vincetoxicum calcaratum (Benth.) Kuntze, Revisio Generum Plantarum 2: 424(1891). Tylophora calcarata Benth., Flora Australiensis 4: 335(1868), Type: Queensland. Rockhampton, Thozet 510; holo: K; iso: MEL.

RFK Code

2562