Hymenodictyon (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Hymenodictyon Wallich

Protologue: Roxb., Fl. ind. 2: 148 (1824).

Family: Rubiaceae

Chromosome number: x= probably 11;H. orixense:n= 22, 33, 2n= 22

Vernacular names

• Indonesia: bindung gelatah (Madura), jati awang, klepu sapi (Java)
• Malaysia: lepar, medang keladi (Peninsular)
• Philippines: aligango, hibau (Tagalog), kukun-banuk (Panay Bisaya). Burma (Myanmar): kusan kuthan
• Cambodia: oulok
• Thailand: lata, som lu (peninsular), som kop (northern)
• Vietnam: cây tai nghé.

Origin and geographic distribution

Hymenodictyon comprises about 20 species, most of which occur in tropical Africa and Madagascar. Only a few species are found in Asia. Probably the only Malesian species is Hymenodictyon orixense (Roxb.) Mabberley (synonyms: Cinchona orixensis Roxb., Cinchona excelsa Roxb., Hymenodictyon excelsum (Roxb.) Wallich ex Roxb.) which occurs in India, Burma (Myanmar), Indo-China, Thailand, Peninsular Malaysia, Sumatra, Java, the Lesser Sunda Islands, the Philippines, Sulawesi and the Moluccas.

Uses

The wood of H. orixense is used locally in house building, e.g. for planks, and sometimes for boats; it is also used for boxes, scabbards, packing-cases, implements, toys and matches. In India it has been recommended for cheaper grades of furniture, warper bobbins and wood-wool board.

In India the bitter bark is used in local medicine as an astringent and febrifuge.

Production and international trade

The wood of H. orixense is probably used rarely and on a local scale only, due to its comparative rareness and patchy occurrence.

Properties

H. orixense yields a lightweight hardwood with a density of 370-540(-610) kg/m³at 15% moisture content, the higher value for a sample from Burma (Myanmar). Heartwood white when fresh, becoming yellow-grey or pale grey-brown on exposure, not clearly demarcated from the sapwood; grain straight; texture moderately fine to slightly coarse and even. Growth rings visible but inconspicuous, boundary marked by a narrow layer lacking parenchyma; vessels medium-sized to moderately large, solitary and in radial multiples of 2-3, occasionally in small clusters, open; parenchyma very abundant, apotracheal diffuse-in-aggregates, sometimes forming more or less continuous concentric layers, visible with a hand lens, occasionally paratracheal; rays extremely fine and moderately fine; ripple marks absent.

Air seasoning is easy: it takes 13 days to kiln dry boards 2.5 cm thick from 80% to 8% moisture content. The wood is soft to moderately hard and moderately strong. It works very easily and turns well. The wood is not durable when exposed to the weather or in contact with the ground and is moderately resistant to preservative treatment. It is somewhat liable to borers, especially when left debarked.

The bark contains scopoletin and a very bitter glycoside.

See also the table on microscopic wood anatomy.

Botany

A small to medium-sized tree up to 25 m tall; bole usually rather straight, up to 50 cm in diameter; bark surface smooth, greyish-brown. Leaves opposite, simple, entire, obovate or ovate to elliptical-lanceolate, with scattered minute hairs all over the upper surface; stipules ovate, with tiny teeth-like glands on the margin. Inflorescence terminal, paniculate, reflexed but with the lateral branches curving upwards. Flowers 5-merous; calyx lobes minute; corolla trumpet-shaped, short-hairy outside; stamens inserted in the throat of the corolla tube, filaments minute; ovary inferior, 2-locular with many ovules. Fruit an ellipsoid, 2-valved, loculicidal capsule, many-seeded. Seed flat and winged all around. Seedling with epigeal germination.

Shoot development is very slow during the first year but the roots may attain 45 cm. Maximum height attained in 4 years in India was only 1.5 m. In India a wood sample from a 41-year-old tree showed a mean annual diameter increment of 0.8 cm, which is fairly high. Trees are only deciduous in very dry regions. Seed can be dispersed over a long distance by wind.

Hymenodictyon belongs to the tribe Cinchoneae of the subfamily Chinchonoideae . The three species of Hymenodictyon reported for the Malesian region may well prove to represent only a single one.

Ecology

Regeneration is usually confined to open spaces in the forest, which may explain why H. orixense is more frequent in (but not restricted to) drier areas where the forest is more open than in the rain forest. In the Philippines it is often found in secondary forest at low and medium altitudes and on cliffs near the sea.

Silviculture H. orixense can be propagated by seed, but direct seeding is not recommended as the seed is very small (about 170 000 seeds/kg) and easily washed away. Seed usually germinates easily, but loses its viability within a year. It should be sown in seed-beds and lightly covered with fine soil or fine sand and watered frequently, but sparingly. The first seedlings appear after 10 days. When 2-3 months old they can be pricked out into containers. The more vigorous seedlings can be planted out after one year, others should be kept in the nursery for another year. H. orixense is suitable for plantations in areas with a mean annual rainfall of 1000-1200 mm. Seedlings are light-demanding and easily killed by weeds. Planting in the open may present some problems. H. orixense is not resistant to fire.

Genetic resources and breeding

H. orixense is widespread although not common in many areas. In Malesia records are scarce and its distribution is very patchy. Some caution in logging this tree seems justified.

Prospects

H. orixense is too scarce in Malesia to be of future importance. However, it might be worthwhile to establish trials of this timber tree, particularly in drier areas, as its timber is considered very useful in India and Burma (Myanmar).

Literature

70, 150, 163, 256, 267, 364, 436, 728, 772, 861, 933, 934, 1052, 1104, 1142, 1221.

E. Boer & R.H.M.J. Lemmens