ThHomonoia

Flora of Thailand

Euphorbiaceae

47. Homonoia

P.C. van Welzen

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Homonoia

Lour., Fl. Cochinch.: 636. 1790; Müll.Arg. in DC., Prodr. 15, 2: 1022. 1866; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.xi: 114. 1919; Airy Shaw, Kew Bull. 26: 282. 1971; Whitmore, Tree Fl. Mal. 2: 102. 1973; G.L.Webster, Ann. Missouri Bot. Gard. 81: 90. 1994; Welzen, Blumea 43: 137. 1998; Radcl.-Sm., Gen. Euphorbiacearum: 239. 2005; Welzen in Welzen & Chayam., Fl. Thailand 8, 2: 336. 2007; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11: 130, Fig. 30. 2014.— Lumanaja Blanco, Fl. Filip.: 821. 1837.— Spathiostemon Blume sect. Haematospermum Baill., Étude Euphorb.: 293. 1858.— Homonoia Lour. sect. Haematospermum (Baill.) Müll.Arg. in DC., Prodr. 15, 2: 1022. 1866.

Shrubs (to small trees), rheophytic, usually dioecious. Indumentum consisting of simple hairs and scale hairs. Stipules caducous. Leaves alternate, simple; blade symmetric, coriaceous, willow-shaped, base acute, margin serrate, with a gland in each tooth at the lower surface, apex acute, very apex mucronulate, lower surface papillate, with scale hairs; venation pinnate, looped and closed near the margin, reticulate. Inflorescences solitary axillary spikes, usually only with staminate or pistillate flowers, occasionally with basal flowers staminate and apical ones pistillate; one flower per node. Flowers actinomorphic, sessile, without petals and disc. Staminate flowers: sepals 3; stamens united into an androphore from which dichotomously splitting branches separate alternately, anthers more than 100; pistillode absent. Pistillate flowers: sepals 5 (or 6), imbricate; ovary 3-locular, ovules 1 per locule. Fruits ovoid rhegmas, small, sericeous outside, glabrous inside; wall thin, woody. Seeds covered by a red arillode.

Two species, one restricted to Central India, the other widespread from India to China and Taiwan, throughout Malesia to New Guinea (on Borneo only found in Sabah); one species in Thailand. Classification: Acalyphoideae, tribe Acalypheae, subtribe Lasiococcinae.

Homonoia riparia Lour., Fl. Cochinch.: 637. 1790; Müll.Arg. in DC., Prod. 15, 2: 1023. 1866; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.xi: 114, fig. 27a-e. 1919; Gagnep. in Lecomte, Fl. Indo-Chine 5: 330, fig. 38: 5–8. 1925; Airy Shaw, Kew Bull. 26: 282. 1971; Whitmore, Tree Fl. Mal. 2: 103. 1973; Steenis, Rheoph. World: 241. 1981; Welzen, Blumea 43: 138, fig. 2, map 1. 1998; in Welzen & Chayam., Fl. Thailand 8, 2: 337, Fig. 8, Plate XVIII: 2. 2007.

Shrubs (to small trees) up to 2(–7) m high. Stipules: 4.8–6.5 by 0.5–1.2 mm. Leaves: petiole 4–13 mm long; blade narrowly elliptic (to obovate), 3.5–21 by 0.5–2.5 cm, index 5–14, above dark green, below silvery to whitish to glaucous, venation raised on both sides, nerves 13–16 per side. Inflorescences up to 7(–10) cm long, dirty green-yellow with a reddish tinge. Staminate flowers 4.5–5 mm in diameter; sepals ovate to elliptic, 2.8–4.3 by 0.8–3.3 mm, outside dark red, inside very pale reddish pink; androphore 3–5.8 mm high, white, connective dark red, anthers c. 0.4 by 0.2 mm, white to yellow. Pistillate flowers c. 2 mm in diameter; sepals ovate, 1.1–2.3 by 0.4–1.1 mm, dull green tinged reddish; ovary globose, 0.8–2 by 0.7–2 mm, style 0(–0.3 mm long, cream), stigmas 1.4–4 mm long, red-brownish. Fruits 3.2–4.5 by 2.7–4 mm, (yellowish red to) brown (to blackish); wall thin, less than 1 mm thick. Seeds 1.3–1.8 by 1.8–2.2 by 1–1.5 mm.

T h a i l a n d.— NORTHERN: Mae Hong Son, Chiang Mai, Chiang Rai, Lampang, Phrae, Nan, Tak, Sukhothai, Phitsanulok; NORTH-EASTERN: Phetchabun, Loei, Khon Kaen; EASTERN: Nakhon Ratchasima; CENTRAL: Nakhon Nayok; SOUTH-EASTERN: Prachin Buri, Chanthaburi, Trat; SOUTH-WESTERN: Uthai Thani, Kanchanaburi, Ratchaburi; PENINSULAR: Chumphon, Surat Thani, Trang, Yala, Narathiwat.

D i s t r i b u t i o n.— Bhutan, India, Sri Lanka, Myanmar, China, Taiwan, Laos, Cambodia, Vietnam (type), Thailand, and throughout Malesia (on Borneo Sabah only), but rare towards the east (Moluccas, New Guinea).

(inset: Homonoia retusa (Wight) Müll.Arg.)

E c o l o g y.— 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; soil: limestone, rocks (gravel), sand. 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. Altitude: sea level up to 700 m.

V e r n a c u l a r.— Khrai (ไคร้), khrai nam (ไคร้น้ำ) (Northern); hia-thi (เหี่ยที้), si-thi-kho (สี่ที่โค่) (Karen-Mae Hong Son); khrai hin (ไคร้หิน), rae (แร่) (Chumphon); ka-lae-rae (กะแลแร) (Malay-Yala), klae-rae (แกลแร) (Malay-Narathiwat).

U s e s.— 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 clear 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 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. Due to the elaborate and large root system the plant is used in N. Sumatra 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. The leaves are used for forage in Vietnam. The root is used to make bolo handles (Sabah, N. Borneo).