Homonoia riparia Lour.

Homonoia riparia Lour.

Family

Euphorbiaceae

Synonyms

Adelia neriifolia Heyne ex Roth, Lumanaja fluviatilis Blanco, Rici­nus salicinus Hassk.

Vernacular Names

Malaysia Kelereh, mempenai, kayu suarah.
English

Water-willow.

Indone­sia Sobah (Javanese), jurai (Sundanese), sangkir (West Sumatra).
Philippines

Agukuk, agoyoi, mana­gos (Tagalog).

Myanmar

Momakha.

Cambodia Réi tuk.
Laos

Kh'aiz fa:d.

Thailand

Khrai-nam, khrai-hin (peninsular), khrai (central, northern).

Vietnam

Ru ri, ri ri, cay ru ri nuoc.

Geographical Distributions

Homonoia ri­paria is widely distributed in Asia from India through Indo-China and southern China to Tai­wan and from Peninsular Malaysia, throughout Indonesia and the Philippines to Papua New Guinea.

Description

Homonoia ri­paria is a gregarious shrub or small, crooked and twisted tree that can grow 1-4 m tall and up to 10 cm in stem diametre. It forms a woody, deep and extensive root system. The branches are smooth to slightly grooved.

The leaves are arranged alternate and simple. The stipules are keel-like, en­larged at base, measure 5-6 mm long and caducous. The petiole is 5-15 mm long and pubescent. The blade is narrowly lance-shaped to oblong, measuring 4-20 cm x 1-2.5 cm, obtuse or rounded at the base, acuminate, obtuse or mucronate at apex, bright green, penninerved, thin and chartaceous. The upper surface is shiny and smooth while the lower sur­face is pubescent, closely becoming hairless, minutely lepidote and with entire or dentate margin.

The male inflores­cence is an axillary and densely-flowered spike. It is 5 cm long or more and pubescent. The peduncle is grooved, with triangular bracts and acuminate. The flowers are solitary, axillary, and with two lateral and sterile bracteoles. The 3 sepals are minute and mucronate. Numerous stamens are united in fascicles or bundles into a connate into a common trunk at the base. The female inflorescence is an elongated, pauciflorous spike and measures up to 7 cm long. The flowers are sessile, axillary and bracteate. There are 5 ovate sepals measuring 1.5-2 mm long. They are acuminate, imbricate and abaxially hairy. The ovary is spherical, trilocular and measures 2 mm in di­ametre. The style is divided into 3 parts. It is 5 mm long, strongly papil­late and basally united over a short distance.

The fruit is a spherical capsule which is 4 mm in diametre, hairy and tricoccous. The seed is 2 mm long, ovoid and crustaceous.

Ecology / Cultivation

Homonoia riparia is restricted to river banks, lake shores and rocky stream beds, from 50-500 m altitude. In its natural habitat, it is regularly flooded, at least annually. Its extended root sys­tem protects it against uprooting during floods; even floods that completely submerge the shrub during the rainy season for up to 9 months per year can be withstood (such plants are called 'rheophytes'). It is found under ever-wet and seasonal climatic conditions, preferring exposed sunny sites on stream banks and in stream beds in streams not too deep or too swift. As to the streambed soil, H. riparia seems to have no preferences; it occurs on sand, granite, shale, andesite, and other volcanic ­derived material, but also on calcareous soil.

Line Drawing / Photograph

h.riparia2

References

  1. Plant Resources of South-East Asia No.11: Auxiliary plants.