Willughbeia coriacea (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Willughbeia coriacea Wall.

Protologue: Apocynaceae

Synonyms

Willughbeia firma Blume, W. minutiflora (Pierre) K.Schum., W. nodosa (Pierre) K.Schum.

Vernacular names

• Borneo rubber (En)
• Indonesia: getah susu (south-western Sumatra), dango, tampirik (south-eastern Kalimantan)
• Malaysia: akar gegerit besi, akar garu
• Thailand: khui, aa-kaa kue-loh (peninsular).

Distribution

Thailand, Malaysia, Indonesia (Sumatra, Java, Kalimantan), Brunei.

Uses

Until about 1900 expectations of W. coriacea were great and in many places plantations were started because the latex yielded a good quality rubber: the best of all the lianas. As soon as the para rubber tree appeared however, it overshadowed all other latex producers and commerial interest in other latex sources disappeared. Medicinally the latex and dried powdered fruits are used to cure ulcers. The bark is used to cure headache and to stop bleeding and a decoction of the root is applied against dysentery. Ripe fruits are edible.

Observations

Woody, glabrous climber, stem up to 30 m long and 10 cm in diameter, containing latex. Leaves opposite; petiole up to 4 cm long; blade elliptical to obovate, 3-30 cm × 1-10 cm, base cuneate to rounded, apex acute to acuminate. Inflorescence an axillary cyme, up to 3 cm long, with 3-25 flowers; flowers 5-merous, bisexual, white or yellow, rarely tinged with red; corolla tubular, tube up to 8 mm long, lobes 4-10 mm long. Fruit a globose to ellipsoidal berry, up to 12 cm × 7 cm, green, yellow or orange. Seed compressed ovoid, about 1 cm long and wide; coma absent. W. coriacea occurs in primary and secondary forest, up to 1600 m altitude, in well drained soils not suffering from stagnant water. The plant grows slowly and yields little compared to the para rubber tree. A 6 -year-old liana yielded 0.1 kg rubber, a 14-year-old one 2 kg. The rubber is white and very elastic when pure and is difficult to mix with latex of other species; adulterations can easily be seen when the rubber is cut. The loss from latex to rubber is about 50% (a great portion is resin).

Selected sources

5, 11, 20, 23, 27, 31, 34, 42.