Erythroxylum (PROSEA Timbers)

Plant Resources of South-East Asia Introduction

List of species

Erythroxylum P. Brown

Protologue: Civ. nat. hist. Jamaica: 278 (1756).

Family: Erythroxylaceae

Chromosome number: x= 12; E. coca, E. novogranatense: 2n= 24

Vernacular names

• Merpitas (trade name)
• Malaysia: chinta mula, ketai mula (Peninsular), perapat burong (Malay, Sabah).

Origin and geographic distribution

Erythroxylum comprises about 200 species which occur throughout the tropics, but most of them are found in South America. The genus is present throughout the Malesian region with only 4 native species and 2 introduced ones.

Uses

The wood of Erythroxylum has been applied for fence posts and poles, flooring and sometimes for local house building, bridges, boat building and tool handles.

The leaves of E. cuneatum are used as a fish poison in the Philippines. Leaves of E. ecarinatum have been used medicinally. E. cuneatum is also planted as an ornamental. The introduced species E. coca Lamk and E. novogranatense (Morris) Hieron. are well-known sources of cocaine that is used as a stimulant and as an anaesthetic, especially in eye surgery.

Production and international trade

Erythroxylum timber is of local use only, as the supplies are very limited.

Properties

Erythroxylum yields a medium-weight to heavy hardwood with a density of 720-1010 kg/m³at 15% moisture content. Heartwood rose-brown, sharply demarcated from the pale yellow-brown sapwood, which is 2.5 cm wide; grain straight or shallowly interlocked; texture rather fine and even. Growth rings indistinct, although occasional darker lines (zones without vessels) suggest growth ring boundaries; vessels moderately small to medium-sized, very numerous, solitary, in radial multiples of 2-4(-8) and in clusters, tyloses present; parenchyma rather sparse, paratracheal vasicentric, aliform to confluent, indistinct with a hand lens; rays very fine, just visible with a hand lens; ripple marks absent.

The wood is hard and is easy to work and to saw, although cutter knives are rapidly blunted due to the abundance of crystals. It is non-durable. The sapwood is rarely susceptible to Lyctus .

The mean fibre length of E. cuneatum from Sumatra is 1.295 mm. Leaves of E. cuneatum contain alkaloids. The principal alkaloid in leaves of E. ecarinatum is tropacocaine.

See also the table on microscopic wood anatomy.

Botany

Evergreen or sometimes deciduous, small to fairly large trees up to 40(-45) m tall, with white latex in leaves and ripe fruits; bole often short and gnarled, up to 55(-65) cm in diameter, sometimes with buttresses; bark surface smooth to closely longitudinally fissured or scaly, somewhat flaky, whitish-brown to greyish or reddish-brown, inner bark fibrous, yellow to pink or reddish-brown mottled; young branches compressed, lenticellate. Leaves alternate, often distichous, simple, entire, often with 2 longitudinal lines on the upper surface; stipules triangular, clasping the twig, caducous. Flowers axillary, solitary or in a cluster, small, bisexual, often heterostylous, 5-merous; calyx campanulate; petals white to yellow, with appendages on the inner side; stamens 10, fused below into a tube; ovary superior, (1-)3-locular with 1 ovule in each cell, styles 3. Fruit a drupe with 1 fertile and 2 enlarged sterile locules, ripening bright red. Seed flattened, curved. Seedling with epigeal germination; cotyledons emergent, linear; hypocotyl elongated; leaves arranged spirally at first, becoming distichous later.

In Peninsular Malaysia trees of E. cuneatum flower for a month during the dry season in April or May, with a possible second flowering period in November to February. In Papua New Guinea E. cuneatum flowers mostly from September to February and fruits from March to September, whereas E. ecarinatum bears flowers and fruits throughout the year. Fruits ripen in 3-4 months. They float in water but are probably mainly dispersed by monkeys, porcupines and cassowaries.

Ecology

Erythroxylum trees occur scattered or sometimes gregariously in primary and secondary forest, up to 2000 m altitude, from the seashore inland, including beach forest, evergreen rain forest, limestone forest, peat-swamp forest and kerangas. In Johore (Peninsular Malaysia) E. cuneatum is a characteristic element of the Syzygium grande (Wight) Walp. coastal forest.

Silviculture In a germination trial in Peninsular Malaysia 6 out of 9 seeds of E. cuneatum germinated in 39-75 days.

Genetic resources and breeding

There are no records of Erythroxylum in seed or germplasm banks. As the utilization of its timber is limited, present logging will hardly affect the genetic resource base.

Prospects

The utilization of Erythroxylum wood is insignificant and will not be encouraged since tools are rapidly blunted when working this timber.

Literature

61, 162, 163, 198, 209, 267, 304, 310, 341, 403, 436, 464, 745, 770, 824, 829, 831, 861, 1037, 1038, 1048, 1221, 1232, 1242.