Xanthophyllum affine is a member of the Polygalaceae, a family represented by 5 genera (Epirixanthes, Polygala, Salomonia, Securidaca and Xanthophyllum), 37 species and 4 subspecies in Peninsular Malaysia. The Polygalaceae is an interesting family because its flowers resemble those of the Leguminosae due to parallel evolutionary specialisation to insect pollination. The flowers of Xanthophyllum are weakly asymmetric and resemble those of the Caesalpinioideae, while the flowers of the other genera resemble those of the Papilionatae.
Xanthophyllum is derived from the Greek words ‘xanthos’ which means yellow and ‘phyllum’ meaning leaf and refers to the leaves that dry yellowish in many species. This coloration is due to the high aluminium content in the tissues. Most species occur in Malesia but also extend as far south as Australia and as far north as southern India. In Peninsular Malaysia, Xanthophyllum is popularly known by its Malay name ‘Minyak berok’, and for Xanthophyllum affine, the Malay names are ‘gading jantan’, ‘lima berok jantan’ and ‘lima berok puteh’.
Out of the 25 species of Xanthophyllum in Peninsular Malaysia, Xanthophyllum affine is the most common. It occurs throughout Peninsular Malaysia from the lowlands and freshwater swamps up to about 1700 m altitude in mountains. It favours forest margins, thickets and river-banks.
Xanthophyllum affine is characterised as a small to big tree (rarely a shrub elsewhere) up to 30 meters tall with a bole to 68 cm diameter. The grey bark is smooth with a rugulose to finely lenticellate surface. The twigs are mostly very densely minutely greyish hairy or glabrescent. The lamina is elliptic to oblong-elliptic (rarely ovate), 6–27 × 2.8–10 cm, with a narrowed base (rarely rounded) and acuminate apex. Pitted glands are nearly always present on the underside of the lamina. The midrib is prominent above and thicker than the 4 to 12 pairs of secondary veins. The tertiary veins are ladder-like. When dry, the lamina is grey-green to bright yellow-green. The inflorescences are racemes up to 20 cm long. The flowers are slightly asymmetric with one of the five petals developed into a keel. The petals are white or yellow (or rarely pink elsewhere) and the upper petal has an orange-yellow spot. The keel is hairy but the other petals are glabrous or only hairy towards the base. The young fruits are ovoid becoming round and creamy to brown when mature. They are single-seeded.
Regarding uses, the timbers of several Xanthophyllum species (including Xanthophyllum affine) are suitable for medium construction under cover. It is also suitable for flooring, planking, veneer and plywood, furniture, sport goods and tool handles.
