Malesian Euphorbiaceae Descriptions

98. SYNDYOPHYLLUM (Euphorbiaceae)


P.C. van Welzen


Welzen, P.C. van. 1995. Taxonomy and phylogeny of the Euphorbiaceae tribe Erismantheae G.L.Webster (Erismanthus, Moultonianthus, and Syndyophyllum). Blumea 40: 375–396.


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Genus description

Key to the species

Species descriptions


Syndyophyllum Lauterb. & K.Schum.


    Syndyophyllum Lauterb. & K.Schum. in K.Schum. & Lauterb., Fl. Schutzgeb. Südsee (1901) 403; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.iii (1911) 104; Airy Shaw, Kew Bull. 14 (1960) 392; Kew Bull. Add. Ser. 4 (1975) 199; Kew Bull. Add. Ser. 8 (1980) 204; Kew Bull. 36 (1981) 349; G.L.Webster, Ann. Missouri Bot. Gard. 81 (1994) 67; Welzen, Blumea 40 (1995) 389; Radcl.-Sm., Gen. Euph. (2001) 123; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11 (2014) 108. — Type: S. excelsum Lauterb. & K.Schum.


Tree, monoecious, branching sympodially. Indumentum consisting of simple, hirsute or sericeous hairs, glabrescent. Stipules small, interpetiolar, triangular, base broad, caducous, esp. outside sericeous. Axillary buds in the axils of leaves or on the petiole of one of the leaves. Petiole reniform in transverse section, not pulvinate, hirsute to sericeous. Leaves simple, distichous, opposite, symmetric; blade chartaceous, punctate; base slightly oblique, acute to broadly attenuate; margin slightly serrate, flat, with a gland in each tooth; apex rounded to acuminate, very apex usually mucronulate; upper surface pustular with white dots, latter forming food bodies in young leaves; lower surface smooth; venation pinnate, looped and closed near the margin, with 2 pairs of footnerves of which one rather indistinct, above and below slightly raised, tertiary (and quaternary) veins finely scalariform. Inflorescences axillary thyrses, one per axil, hardly branching, flattened, with (dichasial) groups of staminate flowers, often with one pistillate flower in between, latter mainly developing after the staminate flowers dropped off. Bracts and bracteoles usually minute, triangular, mainly outside sericeous. Pedicels very short, only in fruit elongating. Flowers actinomorphic. Sepals 4 or 5, imbricate, basally united for at most 1/3, in staminate flowers membranous, in pistillate flowers basally thickened and margin membranous, often some with one or two glands along the margin, outside sericeous, inside (sub)glabrous. Petals shorter than sepals, absent in pistillate flowers and perhaps absent in S. excelsum, in S. occidentale 2–4, ovate to obovate, apex rounded or irregular, membranous, glabrous. Disc lobes absent. Stamens in staminate flowers only, 4 or 5 or 8–10, on short torus, in two whorls, outer whorl epipetalous, free; filament filiform, glabrous; anther ± triangular, basifixed in deep cleft, opening latro-intrors with a slit, glabrous; connective with an apical triangular appendix. Pistil in pistillate flowers: ovary 3-locular, densely hirsute; ovules one per locule, descending, epitropous, anatroupous, atteched in upper half of column; style 1, short, hirsute; stigmas 3, apically split into two lobes, above with papillae, below hirsute; in staminate flowers at most 1 or 3 filiform stigmas. Fruit a 3-lobed rhegma, subglobose, outside sericeous, glabrescent, inside glabrous, dehiscing septi- and loculicidally into 6 segments; wall thin, woody; septum with one splitting vein; column after dehiscense with a narrow, straight septum margin attached to it, apically broadened. Seeds 1–3 per fruit, brown, glossy, micropyle well visible; arilloid absent. Embryo immature, no endosperm.

    Distribution — Two species endemic in Malesia, one in N Sumatra and Borneo, the other in N New Guinea.

    Notes — 1. The branching system in Syndyophyllum and Moultonianthus is very complex (ee note 1 under Moultonianthus). In Syndyophyllum the axillary buds are in the axils of the leaves. However, in S. excelsum one of the axillary buds per leaf pair is formed on a petiole, the other petiole has the axillary bud at its base. The position of the 'budding' petiole alternates per leaf pair.

2. The differences between the species may be larger. However, only one poorly flowering specimen of S. excelsum was examined, which seemed to lack petals and which had fewer stamens.


Key to the species



Per leaf pair one axillary bud halfway on a petiole. Leaves ovate (to elliptic), subglabrous to hirsute below. (Only sepals (or petals) present in staminate flowers. Stamens 4 or 5 ) — New Guinea.

1. Syndyophyllum excelsum


Axillary buds in axil of leaves. Leaves (ovate to) elliptic, subglabrous below. (Sepals and petals present in staminate flowers. Stamens 8–10) — Sumatra, Borneo.

2. Syndyophyllum occidentale


1. Syndyophyllum excelsum Lauterb. & K.Schum. 


    Syndyophyllum excelsum Lauterb. & K.Schum. in K.Schum. & Lauterb., Fl. Schutzgeb. Südsee (1901) 404; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.iii (1911) 105, fig. 33; Airy Shaw, Kew Bull. 14 (1960) 393; Kew Bull. Add. Ser. 4 (1975) 199; Kew Bull. Add. Ser. 8 (1980) 204; Kew Bull. 36 (1981) 350; Welzen, Blumea 40 (1995) 391, Fig. 4, Map 3. — S. excelsum Lauterb. & K.Schum. subsp. excelsum: Airy Shaw, Kew Bull. Add. Ser. 8 (1980) 204. — Type: Lauterbach 2261 (B, holo, †; iso in K), Kaiser Wilhelmland (= N Papua New Guinea).


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Tree, up to 32 m high, d.b.h. up to 1.1 m, bole slightly fluted or with buttresses of c. 0.7 by 0.7 m; flowering branches 1.7–2 mm thick, smooth to pustular, hirsute in Papua New Guinea. Outer bark midbrown to red-brown to brownish black, smooth, dehiscing in irregular flakes, 0.5–1 mm thick; inner bark red to reddish brown, brittle, 3–4 mm thick. Sapwood yellow-brown to orange to dark brown, 2–3 cm thick; heartwood orange-yellow to brown to red-black. Axillary bud of one leaf pair on petiole of leaf. Leaves: stipules 3.2–4.9 by 1–1.2 mm, margin entire, apex acute; petiole 4–9 mm long, hirsute esp. in Papua New Guinea; blade ovate (to elliptic), 6–25 by 2.5–9.5 cm, index 2.2–3.8, apex rounded, mucronulate, above glabrous, glaucous when dry, below subglabrous to hirsute in Papua New Guinea, brown when dry, nerves 10–12 per side. Inflorescences up to 15.3 cm long, densely hirsute in Papua New Guinea. Bracts to the flowers 1.5–2.1 by 0.6–1.1 mm, outside hirsute; bracteoles to the flowers c. 0.8 by 0.3 mm, outside hirsute. Staminate flowers c. 2 mm in diam.; pedicel more or less absent; sepals (or petals) 4, ovate, 0.8–1.2 by 0.3–0.6, subsericeous; petals probably absent; stamens 4 or 5, filament c. 2.2 mm long, anther c. 0.8 by 0.8 mm. Pistillate flowers not seen. Fruits c. 14 mm broad by 8 mm high; pedicel up to 7 mm long; wall c. 0.8 mm thick. Seeds ± globose, 7–8 mm in diam.; hilum c. 0.8 mm long. Embryo not seen.

    Distribution — Malesia: N New Guinea (N Irian Jaya and N Papua New Guinea).


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    Habitat & Ecology — Found in primary rainforest. Reasonably common to scarce. Soil: Sandy clay, peath. Altitude: 30–520 m. Flowering: June; fruiting: October.

    Vernacular names — New Guinea, Irian Jaya: Besoembrij, kegboi, sekaidjakka, siekoe, wobbryka (Manikiong); kelasawa, kloesaoe, kloesawa, koeloesawa (Mooi); ktoem (Kebar); makan (Kwerba); menom (Hattam). --- Papua New Guinea: Dabi, falef, pispis, sab (Amele); djakui, dumpahop, dzara, hawamp, malamamoi, sankei, sarenki, sisek, sumpiam (Dumpu); dumusi, mames, panama (Bilia); fai, golo, mont, sogi, wime (Faita).

    Note — The specimens from Papua New Guinea are very hirsute on branches, leaves, and inflorescences, while the Irian Jaya specimens are more subglabrous like the W Malesian S. occidentale.


2. Syndyophyllum occidentale (Airy Shaw) Welzen 


    Syndyophyllum occidentale (Airy Shaw) Welzen, Blumea 40 (1995) 393, Fig. 4, Map 4. — Syndyophyllum excelsum Lauterb. & K.Schum. subsp. occidentale Airy Shaw, Hooker's Icon. Pl. 38 (1974) tab. 3722; Kew Bull. Add. Ser. 4 (1975) 199; Kew Bull. 36 (1981) 350, fig. 10. — Type: SAN (Meijer) 53229 (K, holo), Borneo, Sabah, Sandakan Dist., Sg. Melagatan, near Kuala Mengkabong.

    Excoecaria macrophylla auct. non J.J.Sm.: Merr., Philipp. J. Sc. 24 (1924) 387.


Syndexce-occi-habit.gif (43884 bytes) (right habit)    Syndexce-male.gif (28028 bytes)    Syndexce-female.gif (29276 bytes)    Syndexce-fruit.gif (60476 bytes)


Tree, up to 23 m high, girth up to 1.25 m, d.b.h. up to 40 cm; (buttresses up to 70 cm); flowering branches 1.5–2 mm thick, smooth to pustular, sericeous when young. Outer bark (whitish to purplish) brown to very dark, smooth to lenticellate, scaling in large plates; inner bark dark orange brown to red, c. 6 mm thick, sticky. Sapwood white; cambium yellowish to red. Axillary buds in axils of leaves. Leaves: stipules 3.2–4.9 by 1–1.2 mm, margin entire, apex acute; petiole 6–13 mm long, at most sericeous above in groove; blade (ovate to) elliptic, 8.2–31 by 2.3–12.5 cm, index 2.2–3.8, apex acute to acuminate, very apex rounded to mucronulate, above glabrous, dark green, below subsericeous, yellow-green, nerves 10–12 per side. Inflorescences up to 34 cm long, (sub)sericeous. Bracts to the cymules 1.7–4.4 by 0.7–1 mm, outside hirsute. Staminate flowers 2–3 mm in diam.; pedicel less than 0.5 mm long; sepals 5, ovate, 1.4–2 by 0.5–0.8 mm, subhirsute, esp. the margin, whitish green; petals 2–4, 0.7–1.8 by 0.3–1.1 mm; stamens 8–10, filament 3.5–5.5 mm long, anther c. 1 by 0.7 mm; stigma remnant absent to 3 linear styles, up to 1.5 mm long. Pistillate flowers 2–2.5 mm in diam., pedicel 0.5–1.3 mm long; sepals 5, ovate, 1.2–2.1 by 0.6–1.2 mm, outside sericeous, inside glabrous; ovarium ovoid, 1.3–2.1 by 1.3–2.8 mm broad, style 1–3.5 mm long, stigmas 5–8 mm long, upper 1–2 mm bifid. Fruits 14–19 mm broad by c. 8 mm high; pedicel up to 7 mm long, bright brown; wall c. 0.7 mm thick. Seed ± globose, 6.5–9 mm in diam., dark brown to black; hilum c. 0.8 mm long. Embryo only seen immature, at least 6 by 5.3 mm, radicle c. 0.5 mm long.

    Distribution — Malesia: N Sumatra and Borneo.


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    Habitat & Ecology — Found in primary forests along rivers. Soil: sandstone, black soil. Altitude: 15–600 m. Flowering: March to September; fruiting: May to November. Reported to be associated with ants (Argent et al. 108247); the ants are probably attracted by the food bodies produced by the young leaves on their upper surface.

    Vernacular names — Borneo, Sabah: Bringguati (Dusun Banggi).