Malesian Euphorbiaceae Descriptions

57. HOMONOIA (Euphorbiaceae)


P.C. van Welzen


Welzen, P.C.  van. 1998. Revisions and phylogenies of Malesian Euphorbiaceae: Subtribe Lasiococcinae (Homonoia, Lasiococca, Spathiostemon) and Clonostylis, Ricinus, and Wetria. Blumea 43: 131164.


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Genus description

Species description


Homonoia Lour.


    Homonoia Lour., Fl. Cochinch. (1790) 636; Mll.Arg. in DC., Prodr. 15.2 (1866) 1022; D.Vidal, Sin. Gen. Pl. Lenos. Filip. (1884) 236; Hook.f., Fl. Brit. India 5 (1887) 455; J.J.Sm. in Koord. & Valeton, Meded. Dept. Landb. Ned.-Indi 10 (1910) 542; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.xi (1919) 114; Merr., Enum. Philipp. Fl. Pl. 2 (1923) 447; Ridl., Fl. Malay Penins. 3 (1924) 309; Gagnep. in Lecomte, Fl. Indo-Chine 5 (1925) 330; Corner, Ways. Trees Malaya (1940) 258; Backer & Bakh.f., Fl. Java 1 (1963) 491; H.L.Li, Woody Fl. Taiwan (1963) 430; Airy Shaw, Kew Bull. 26 (1971) 282; Whitmore, Tree Fl. Malaya 2 (1973) 102; Airy Shaw, Kew Bull. Add. Ser. 4 (1975) 136; Kew Bull. Add. Ser. 8 (1980) 121; Kew Bull. 36 (1981) 310; Steenis, Rheoph. World (1981) 240; Airy Shaw, Kew Bull. 37 (1982) 25; Alph. Enum. Euph. Philip. Isl. (1983) 33; G.L.Webster, Ann. Missouri Bot. Gard. 81 (1994) 90; Welzen, Blumea 43 (1998) 137; Radcl.-Sm., Gen. Euphorbiacearum (2001) 239; Welzen in Welzen & Chayam., Fl. Thailand 8, 2 (2007) 336; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11 (2014) 130, Fig. 30. Spathiostemon Blume sect. Haematospermum Wall. ex Baill., tude Euphorb. (1858) 293. Homonoia Lour. subgen. Lumanaja (Blanco) Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.xi (1919) 114, nom. inval. (ICBN, 1994, art. 22.2). Type: Homonoia riparia Lour.

    [Haematospermum Wall., Cat. (1832) 7953, nom. nud. Based on Haematospermum neriifolium Wall., nom. nud. (= Homonoia riparia Lour.)]

    Lumanaja Blanco, Fl. Filip. ed. 1 (1837) 821. Type: Lumanaja fluviatilis [= Homonoia riparia Lour.]


Shrub (to small tree), usually dioecious, also monoecious (see note 1). Indumentum consisting of simple, hirsute to sericeous hairs and scale hairs. Stipules small, triangular to ovate with an asymmetric base, thick, caducous. Leaves spirally arranged, simple; petiole short, kidney-shaped in transverse section, not pulvinate; blade coriaceous, willow-shaped, not punctate, base acute, margin laxly indistinctly (to distinctly) serrate, flat, with a gland in each tooth at the lower surface, apex acute, very apex mucronulate, upper surface smooth, glabrous except for the basal part of the midrib, lower surface papillate in H. riparia, with scale hairs, venation pinnate, looped and closed near the margin, reticulate. Inflorescences solitary axillary spikes, usually only with staminate or pistillate flowers, occasionally spikes with staminate flowers basally and pistillate ones apically; staminate flowers one per node. Bracts and bracteoles ovate to triangular, margin and outside sericeous. Flowers actinomorphic, sessile, without petals and disc, no odour. Staminate flowers: sepals 3, inequal, (sub)glabrous; stamens united into a thick androphore from which branches branch off alternately, branches splitting up dichotomously, ending with an anther, latter more than 100, very small, opening latro-introrsely; pistillode absent. Pistillate flowers: sepals 5 (or 6), imbricate, apex acute, margin and outside sericeous; ovary hirsute, 3-locular, ovules 1 per locule, descending, epitropous, anatropous, axillary, subapically attached to the column, style usually absent, stigmas 3, apically (not) split, stigmatic lobes on upper surface and along margin. Fruit an ovoid to slightly coccoid rhegma, outside sericeous, inside glabrous, dehiscing loculicidally and later also partly septicidally into 3 bivalved segments; wall thin, woody; septa with a basal vein and a vein halfway (at apex of column); column after dehiscence with a narrow straight septum margin, apically tapering, not broadened. Seeds usually 3 per fruit, ovoid, but keeled at one side, somewhat flattened; arillode sarcotesta-like, covering seed completely, red. Embryo flat, without endosperm.

    Distribution 2 species, H. retusa restricted to Central India, H. riparia widespread from India to China and Taiwan, throughout Malesia to New Guinea (on Borneo only found in Sabah).

    Habitat & Ecology Rheophytes, often common and mainly found in and along rivers at low altitudes.

    Note In H. riparia most specimens only show staminate or pistillate flowers, which probably indicates dioecy. Several specimens contain separate branches (perhaps from different plants), each with flowers of one sex, but with both sexes present. A handful of specimens show flowers with mixed inflorescences on the same branch, some with staminate flowers, others with pistillate flowers, and several with staminate flowers basally and pistillate flowers apically. These plants are of course monoecious. Perhaps the species is monoecious and the different sexes appear on the same plant, but separated in time and on different inflorescences.


Homonoia riparia Lour. 


    Homonoia riparia Lour., Fl. Cochinch. (1790) 637; Mll.Arg. in DC., Prodr. 15.2 (1866) 1023; Fern.-Vill., Nov. App. (1880) 196; Hook.f., Fl. Brit. India 5 (1887) 455; J.J.Sm. in Koord. & Valeton, Meded. Dept. Landb. Ned.-Indi 10 (1910) 547; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.xi (1919) 114, fig. 27ae; Merr., Enum. Philipp. Fl. Pl. 2 (1923) 448; Ridl., Fl. Malay Penins. 3 (1924) 309; Gagnep. in Lecomte, Fl. Indo-Chine 5 (1925) 330, fig. 38: 58; Burkill, Dict. Econ. Prod. Malay Penins. 1 (1935) 1186; Corner, Ways. Trees Malaya (1940) 258, fig. 82; W.H.Br., Usef. Pl. Philip. 2, Techn. Bull. Dept. Agric. Philipp. Islands 10 (1950) 311; Heyne, Nutt. Pl. Indonesi 1, 3rd ed. (1950) 932; Backer & Bakh.f., Fl. Java 1 (1963) 492; H.L.Li, Woody Fl. Taiwan (1963) 430, fig. 152; Airy Shaw, Kew Bull. 26 (1971) 282; Whitmore, Tree Fl. Malaya 2 (1973) 103; Airy Shaw, Kew Bull. Add. Ser. 4 (1975) 136; Kew Bull. Add. Ser. 8 (1980) 121; Kew Bull. 36 (1981) 310; Steenis, Rheoph. World (1981) 241; Airy Shaw, Kew Bull. 37 (1982) 25; Alph. Enum. Euph. Philip. Isl. (1983) 33; Welzen, Blumea 43 (1998) 138, Fig. 2, Map 1; in Welzen & Chayam., Fl. Thailand 8, 2 (2007) 337, Fig. 8, Plate XVIII: 2. Type: Loureiro 222 (BM, holo), Cochinchina (Vietnam), Ri ri bo foung.

    Croton salicifolius Geiseler, Croton. Monogr. (1807) 6, non C. salicifolius Gagnep. Type: Vahl's herbarium (ex. Hb. Richard) s.n., s.d. (C), Java.

    Adelia neriifolia Heyne ex Roth, Nov. Pl. Spec. (1821) 375; Wight, Ic. Pl. Ind. Or. 5 (1852) 20, t. 1868. Haematospermum neriifolium (Heyne ex Roth) Wall., Cat. (1832) 7953 Spathiostemon salicinum Baill., tude Euphorb. (1858) 293, nom. superfl. Type: Wallich 7953B (Hb. Heyne) (K, holo; iso in BM, K), India orientalis.

    [Haematospermum riparium Wall., Cat. (1832) 7953, nom. nud. Based on Wallich 7955 (A, K), Assam.]

    Lumanaja fluviatilis Blanco, Fl. Filip. ed. 1 (1837) 821; ed. 2 (1845) 568, ed. 3, 3 (1879) 236, fig. 338. Neotype (designated by Welzen, 1998): Fl. Filip. ed. 3, 3 (1879) fig. 338. Placed in synonymy of H. riparia by Fernndez-Villar (1880).

    Ricinus ? salicinus Hassk., Cat. Hort. Bot. Bogor. (1844) 237; Pl. Java Rar. (1848) 264. Spathiostemon salicinus (Hassk.) Hassk., Hort. Bogor. Descr. (1858) 41. Type: Hasskarl s.n., 1841 (L, holo, no. 904.75-252), Java, Bantam.

    Spathiostemon salicinus (Hassk.) Hassk. var. angustifolius Miq., Fl. Ned. Ind., eerste bijv. (1860) 452. Syntypes: Diepenhorst HB 552 (U), Sumatra, Lubu-alang; Diepenhorst HB 1397 (U), Sumatra, Priaman; Teijsmann HB 4341 (U), Sumatra, Lampong Prov., Tega-nennin.


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Shrub (to small tree), up to 2(7) m high, d.b.h. up to 15 cm; flowering branches 25 mm thick, smooth to slightly ribbed, lenticular, sericeous. Outer bark grey-brown to red-brown, smooth to horizontally and vertically fissured; corky middle bark red; inner bark green to cream. Sapwood white, hard. Leaves: stipules 4.86.5 by 0.51.2 mm, margin entire, apex acute, margin and upper surface glabrous except for some basal scale hairs, lower surface hirsute; petiole 413 mm long; blade elliptic (to somewhat obovate), 3.521 by 0.52.5 cm, index 514, above dark green, below silvery to whitish to glaucous, venation raised on both sides, nerves 1316 per side. Inflorescences up to 7(10) cm long, dirty green-yellow with a reddish tinge. Bracts 12.2 by 0.71.7 mm; bracteoles 0.61.5 by 0.31 mm. Staminate flowers 4.55 mm in diam.; sepals ovate to elliptic, 2.84.3 by 0.83.3 mm, outside dark red, inside very pale reddish pink; androphore 35.8 mm high, white, connective dark red, anthers c. 0.4 by 0.2 mm, white to yellow. Pistillate flowers c. 2 mm in diam.; sepals ovate, 1.12.3 by 0.41.1 mm, dull green tinged reddish; ovary globose, 0.82 by 0.72 mm, style absent (to up to 0.3 mm long, cream), stigmas 1.44 mm long, red-brownish. Fruits 3.24.5 by 2.74 mm, (yellowish red to) brown (to blackish); wall thin, less than 1 mm thick. Seeds 1.31.8 by 1.82.2 by 11.5 mm. Embryo: cotyledons 1.51.8 by 1.21.5 mm; plumule and radicle c. 0.3 mm long.

    Distribution Widespread, found in Bhutan, India, Sri Lanka, Myanmar, China, Taiwan, Laos, Cambodia, Vietnam, Thailand, and throughout Malesia (on Borneo Sabah only), but rare towards the east (Moluccas, New Guinea). 


Homonoia-map.gif (65170 bytes) (inset: Homonoia retusa (Wight) Mll.Arg.)


    Habitat & Ecology Rheophyte, usually in groups on river banks, in rocky (fast running) stream beds, and along the coast. Soil usually (temporarily) inundated, in some areas for months. Anchorage of the plants superb (Steenis, 1981). Flowers are presumably wind pollinated. The seeds are very hard and durable; they sink in water and may be transported by the river into even the sea, where they can still germinate in salt water along the coast. Soil: limestone, rocks (gravel), sand. Alt.: sea level up to 700 m. Flowering and fruiting throughout the year.

    Uses The plant is used as medicine against different diseases. Laos: decoction of leaves to be used against itch. Cambodia: stem and leaves are used as a medicine to depurate the skin of diseases, young leaves and shoots produce hair oil, and wood is used in an infusion against malaria. Thailand: mashed and powdered leaves are a treatment against skin eruption. Malaysia (N Perak): pounded leaves and fruits are used against skin diseases too, either in a poultice and/or as a decoction to be drunk. Java: Used as a medicine, unknown for which cause; also used to fasten loose teeth. S Philippines: the plant may be a stimulant against certain venereal diseases; a root decoction acts as an emetic, while water running at the foot of the shrubs may have depurative properties.

    Other uses Due to the elaborate and large root system the plant is used in N. Sumatra (Gajo lands; Steenis, 1981) and Java to protect river banks or is planted to prevent erosion. The saps of the plant may dye teeth black (Java). In South China the bark is used as rope (Steenis, 1981). The leaves are used for forage in Vietnam. The root is used to make bolo handles (Sabah, N Borneo). (After Airy Shaw, 1975; W.H. Br., 1950; Burkill, 1935; Heyne, 1950, N.N.Thin, ms.)

    Vernacular names Ceylon: omi, werawala (Singh). Myanmar: kyauk(a)naga, momaka, nyin ye bin. China: shui yeung mui. Laos: kek khay. Cambodia: rey tuck. Vietnam: cy r r nuc, r r, r r. Thailand: k(l)ai nam (Lao); klai hin, mai kerai, (ta)kri nam. Malay Peninsula: willow spurge (English); kalire (Batek); champenai, kelereh, kayu suarah, mempenai, kelerai. Sumatra: sangka, sangkir (Malay); sansang haroes/sesang aroes (Lampung); serkil (Gajo Lands). Java: kajoe soebah, keding djati, soebah/sobah, tambahoea (Javanese); djoerai/joerei/tjoerei/tjurai (Sundanese). Borneo (Sabah): bongai tidong (Idahan); parang-parang (Bajan). Philippines: agooi, agoioi, agukuk, balanti, dumanai, kagoioi, lumanai, lumanaia, apoioi mangagos, managos (Tagalog); baha (Tagbanua); balanti (Zambal); daguwas (S.L. Bis); dumanai (Iloho); hangarai malabugos, miagook, miagus (Bisaya); liuhon (Sambali); mamalis (Ilog). Sulawesi: tidemobugato. Lesser Sunda Islands (Flores): kenga wa, mela wa. (after W.H.Brown, 1950; Corner, 1940; Heyne, 1950; J.J.Smith, 1910, Whitmore 1973; and N.N.Thin, ms.)