Malesian Euphorbiaceae Descriptions

93. SPATHIOSTEMON (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: 131–164.

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Genus description

Key to the species

Species descriptions

Spathiostemon Blume

    Spathiostemon Blume, Bijdr. (1825) 621; Airy Shaw, Kew Bull. 26 (1972) 341; Whitmore, Tree Fl. Malaya 2 (1973) 132; Airy Shaw, Kew Bull. Add. Ser. 4 (1975) 196; Kew Bull. Add. Ser. 8 (1980) 202; Kew Bull. 36 (1981) 345; Kew Bull. 37 (1982) 35; Alph. Enum. Euphor. Philip. Isl. (1983) 45; Welzen, Blumea 43 (1998) 145; Radcl.-Sm., Gen. Euphorbiacearum (2001) 238; Welzen in Welzen & Chayam., Fl. Thailand 8, 2 (2007) 557; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11 (2014) 129. — Spathiostemon Blume sect. Euspathiostemon Baill., Étude Euphorb. (1858) 203, nom. illeg. — Homonoia subgen. Spathiostemon (Blume) Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.ix (1919) 117. — Type: Spathiostemon javensis Blume.

    Polydragma Hook.f., Hook. Ic. Pl. 18 (1887) pl. 1701; Fl. Brit. India 5 (1888) 456. — Type: Polydragma mallotiformis Hook.f. [= Spathiostemon javensis Blume].

Shrubs to trees, monoecious, but sexes flowering at different times; flowering twigs smooth, lenticellate, glabrous except when young. Indumentum existing of simple hairs only. Stipules deltoid, outside hairy, inside glabrous, early caducous. Leaves spirally arranged, simple; petiole relatively long, flattened above, basally and apically somewhat pulvinate; blade papery, usually symmetric, base rounded to cuneate, at margin with 2 or 3 glands at each side, latter sometimes confluent into a glandular zone, margin entire, wavy, apex cuspidate to caudate, very apex rounded to acute and mucronulate, usually green when dry, paler below, nerves looped and joined near margin, usually with hair dot domatia in Sp. javensis, veins scalariform, quaternary veins more reticulate. Inflorescences axillary to pseudoterminal racemes, unbranched, usually one per axil, with either staminate or pistillate flowers, flattened, pendulous when staminate, erect when pistillate; staminate flowers single per node. Bracts and bracteoles broadly ovate to deltoid, forming a cup under each single flower, outside or margin hairy, bracteoles in staminate flowers of especially Sp. moniliformis spreading and cordate. Flowers actinomorphic, petals and disc absent, odour unknown. Staminate flowers sessile to shortly pedicelled; sepals 3, mainly glabrous, with c. 4 obvious nerves; stamens more than 100, very small, united into 4–7 androphores, latter bifurcating into separate stamens; anthers 2-locular, opening latero-introrsely? with lengthwise slits; pistillode absent. Pistillate flowers: pedicel elongating or not, with abcission zone in upper part; sepals 5 or 3+3, margin ciliate; pistil 3-locular, triangular in transverse section, one ovule per locule, smooth or echinate with hairs; style absent to short, stigmas 3, apically not split, glabrous, above with flat, broad papillae. Fruits slightly lobed capsules, outside glabrous, smooth or echinate, woody, thin-walled, septicidally breaking into 3 bivalved parts; column after dehiscence with a narrow, straight, non-fibrous septum margin and a broadened apex, obtriangular in longitudinal section. Seeds usually 2 or 3 per fruit, obovoid, slightly triangular in transverse section; caruncle or arilloid absent; embryos not seen.

    Distribution — 2 Species, one endemic in Peninsular Thailand, the other one ranging throughout Malesia from the Malay Peninsula to Papua New Guinea, though absent from Sumatra.

Key to the species

1. Spathiostemon javensis Blume 

    Spathiostemon javensis Blume, Bijdr. (1825) 622; Baill., Étude Euphorb. (1858) 293; Airy Shaw, Kew Bull. 20 (1966) 45; Whitmore, Tree Fl. Malaya 2 (1973) 132; Airy Shaw,; Kew Bull. Add. Ser. 4 (1975) 196; Kew Bull. Add. Ser. 8 (1980) 202; Kew Bull. 37 (1982) 35; Alph. Enum. Euphor. Philip. Isl. (1983) 45; Welzen, Blumea 43 (1998) 146, Fig. 4a–h, Map 3. — Adelia javanica (Blume) Miq., Fl. Ind. Bat. 1, 2 (1859) 388. — Homonoia javensis (Blume) Müll.Arg., Linnaea 34 (1865) 200; in DC., Prodr. 15, 2 (1866) 1022; J.J.Sm. in Koord. & Valeton, Bijdr. Boomsoort. Java 12: 544; Nova Guinea Bot. 8 (1910) 240; Merr., Philipp. J. Sci. 11 (1916) 283; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.ix (1919) 117, fig. 27f; Backer & Bakh.f., Fl. Java 1 (1963) 492; Kulshreshtha & Ahmed, Feddes Repert. 104 (1994) 362, pl. III, 1. — Spathiostemon javensis Blume var. javensis: Airy Shaw, Kew Bull. Add. Ser. 8 (1980) 202. — Lectotype (designated by Welzen, 1998): Anonymous 1324 (L, sheet no. 904.75-232), Indonesia, Java, Tjiradjas.

    Polydragma mallotiformis Hook.f., Hook. Ic. Pl. 18 (1887) pl. 1701; Fl. Brit. India 5 (1888) 457; Ridl., Fl. Malay Penins. 3 (1924) 310. — Type: Scortechini 1781 (K, holo; iso in K), Malaysia, Perak.

    Mallotus eglandulosus Elm., Leafl. Philipp. Bot. 1 (1908) 313. — Type: Elmer 7152 (PNH, holo, †; iso in A, K, NY), Philippines, Leyte Isl., Leyte Prov., Palo.

    Homonoia javensis (Blume) Müll.Arg. var. ciliata Merr., Philipp. J. Sci. 7 (1912) 391. — Type: FB (Everett) 7246 (n.v.), Philippines, Negros Isl., Cauayan.

    Mallotus calvus Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.vii (1914) 195. — Syntypes: Lauterbach 2855 (B, †; no. 855 in A, K could be identical), Papua New Guinea, Ssigaun; Schlechter 16356 (B, †; no. 16336 in K could be identical), Papua New Guinea, Wobbe; Schlechter 19993 (A), Papua New Guinea, Peso. See also Airy Shaw, Kew Bull. 20 (1966) 45 and note 2.

    Spathiostemon javensis Blume var. nimae Airy Shaw, Airy Shaw, Kew Bull. Add. Ser. 8 (1980) 202. — Type: NGF (Henty) 29378 (BRI, holo, n.v.; iso in K, n.v., L), Papua New Guinea, Morobe Dist., Lae Subdist., trans-Busu, near Sankwep River, 147.05 EL, 6.40 SL.

Shrub to tree, up to 20 m high, d.b.h. up to 45 cm; buttresses seldom present, up to 1 m high and long, 30 cm thick; flowering twigs 1.5–4 mm thick. Bark smooth, fluted, peeling off in scales or strips, white to grey to white mottled to dark red to pale brown to dark brown to black, 0.3–1 mm thick; inner bark 2–3 mm thick, white to yellow to reddish to brown; wood soft to usually hard, sapwood white to brownish, heartwood brownish. Stipules 1–2.4 by 0.8–1.1 mm. Leaves: petiole 0.9–5.5 cm long, subhirsute with long and, less often, short hairs; blade elliptic to somewhat obovate, 4.3–24 by 1.7–11 cm, ratio 1.8–3.2, above smooth, glabrous, below smooth, glabrous except for some hairs on the midrib (to seldom completely subhirsute), venation raised on both sides, with 6-8 pairs of nerves, below usually with hair bundle domatia in axils. Inflorescences hirsute with short and usually long hairs, staminate ones up to 7.3 cm long, pistillate ones up to 3.8 cm long. Bracts and bracteoles 0.8–1 by 1–1.2 mm. Flowers green to white to yellow to brown, often tinged red. Staminate flowers 5.5–6 mm in diam.; pedicel 1–1.3 mm long, subhirsute with short and usually long hairs; sepals ovate to elliptic, 2.7–3.5 by 1.6–2.3 mm, glabrous except for the acute apex; stamens: androphores and filaments up to 5 mm long, white, anthers c. 0.4 by 0.3 mm. Pistillate flowers 2.2–3.8 mm in diam.; pedicel elongating in fruit, up to 8 mm long, subhirsute with short and usually long hairs; sepals 5, triangular to ovate, 1–2 by 0.5–0.8 mm, recurved in older flowers; pistil c. 0.8 by 0.8 mm in young flowers, light cream to yellowish to green, subhirsute and papillate; style absent to 0.9 mm long; stigmas elongating in fruit to 6.5 mm, glabrous, brown. Fruits 1–1.2 by 0.6–0.7 cm, echinate with long papillae with on top various hairs of which one at least longer, glabrescent, pink brownish to reddish to yellow. Seeds 5–5.5 by 4.5–5 mm.

    Distribution — Endemic in Malesia, found in Peninsular Malaysia (Perak), Java, Borneo (especially Sabah), Philippines (except Luzon), Sulawesi, Moluccas, Lesser Sunda Islands, and New Guinea; absent in Sumatra.

(dots in Malesia)

    Habitat & Ecology — Often common in understorey of primary and secondary forest, shrubbery, on cliffs, along rivers, and along and in rubber and cocoa plantations on usually flat to undulating country. Soil dry to periodically inundated, often limestone, also on alluvial, black or brown clay, clay-loam, and sand. Altitude: sea level up to 670 m. Flowering and fruiting whole year through.

    Anatomy — Kulshreshtha & Ahmed (1993) report the wax on the leaves to be granular (plate III, 1).

    Uses — The wood is used for construction in the Philippines and for bridges in sea water on Halmahera (Moluccas).

    Vernacular names — Borneo: Kalimantan: wajan koreng; Sabah: kubur (Dusun Banggi); ansalapan, mengkig, toto (Dusun Kinabatangan); lengkan (K.); kilas (Murud); sengulpid (Sungei); Sarawak: bantas (Iban). Philippines: oyagingon (Manobo); apanang (Waray-waray). Moluccas: Halmahera: obadinga mabedeka (Tobaro). New Guinea: Irian Jaya: megwe (Berik); darmor (Biak); djangere (Iraroetoe); hoekane (Irian); batogara (Kemtoek); boeboekwa, kegboi, sorohok (Manikiong); samakjor (Numfur); pole (Sentani); anan (Wain); boeboeika, menom; Papua New Guinea: ali’es, baulai, kalikal, konos, kulis, o, oluai, on’as, sanam, uk, unase, yehaye (Amele); gale, galud, keka, kisos, menag, ninegsi, niniki (Bilia); asoadzim (Bogia); bisip, dzumpiam, kala, malamamoi, mempong, pasip, sarenki, singas, tumpahop, wasirip (Dumpu); bulim, dabe, gwandere, mai, orare, sariri, tukai, unai, wime (Faita); sarr (Jal).

    Notes — 1. This species is not very variable. In the Philippines the hairy domatia are usually absent. Most variation can be found in New Guinea, where the leaves can become quite small, the hairy domatia can be absent too, and the lower surface of the leaves can be differently coloured (the not accepted var. nimae) or very hirsute.

2. Three syntypes are mentioned for the name Mallotus calvus by Pax and K.Hoffmann (1914). Two of these could not be traced anymore, but the possibility exists that Lauterbach 855 (present in K and a leaf print in A) and Schlechter 16336 (K) were misspelled as Lauterbach 2855 and Schlechter 16356 by Pax and Hoffmann (Airy Shaw, 1966). Both K specimens are Spathiostemon javensis, but due to the problems with the collector numbers the synonym status of M. calvus was still uncertain. The third specimen cited, Schlechter 19993 (duplicate in A), not seen by Airy Shaw, is indeed Sp. javensis. Therefore, Airy Shaw’s interpretation that Mallotus calvus is a synonym of Sp. javensis is correct.

3. The variety ‘nimae’, described by Airy Shaw (1980), based on colour differences in the leaf, cannot be recognized satisfactorily and is therefore treated as a synonym.

2. Spathiostemon moniliformis Airy Shaw 

    Spathiostemon moniliformis Airy Shaw, Kew Bull. 16 (1963) 357; Kew Bull. 20 (1967) 408; Kew Bull. 26 (1972) 341; Hooker’s Icon. Pl. 38 (1974) tab. 3720; Welzen, Blumea 43 (1998) 150, fig 4g–i, Map 3; in Welzen & Chayam., Fl. Thailand 8, 2 (2007) 557, Fig. 83. — Type: Kerr 18162 (K, holo, n.v.; iso in L!), Thailand, Surat, Ban Krut.

    Spathiostemon forbesii non Airy Shaw: Airy Shaw 36 (1981) 345, p.p. pro Thai specimens.

Shrub to tree, up to 10 m high, d.b.h. up to 11 cm; buttresses unknown; flowering twigs 1.5–3 mm thick. Stipules 1–2.4 by 0.8–1.1 mm. Leaves: petiole 1.3–2.8 cm long, glabrous; blade (somewhat ovate to) elliptic, 6.2–26.5 by 2.3–9.5 cm, ratio 1.8–2.7, smooth and glabrous on both sides, venation sunken (to raised) above, raised below, with 4–6 pairs of nerves, domatia in axils absent. Inflorescences (sub)glabrous, staminate ones 6–28 cm long, green; pistillate ones up to 3.3 cm long. Flowers white to yellowish. Bracts 1.1–1.3 by 0.8–1.2 mm; bracteoles: lower larger than inner, 1.1–1.3 by 1.2–2 mm. Staminate flowers sessile; sepals ovate to elliptic, 2.4–2.5 by 1.8–2 mm, glabrous; stamens: androphores and filaments up to 5 mm long, anthers c. 0.4 by 0.3 mm. Pistillate flowers: pedicel c. 0.3 mm long, not elongating in fruit, glabrous; sepals 6, in 2 rows of 3, ovate, outer c. 1.7 by 1.8 mm, thick, keeled, inner c. 1.1 by 1.3 mm, thinner; pistil c. 0.8 by 0.6 mm in young flowers, smooth, glabrous; style absent; stigmas triangular, also in transverse section, glabrous except for apex. Fruits c. 9 by 6 mm, smooth, glabrous, reddish to dark brown. Seeds c. 4.8 by 4 mm.

    Distribution — Endemic in Peninsular Thailand.

(squares in Thailand)

    Habitat & Ecology — Often common in evergreen and secondary forest with evergreen patches. Altitude: 10–200 m. Flowering and fruiting: December to March, August, September.

    Vernacular names — Thailand: Surat Thani Prov.: kha khao, khan laen.