Malesian Euphorbiaceae Descriptions

38. DICOELIA (Phyllanthaceae)

P.C. van Welzen

Welzen, P.C.  van. 2011. Revision of Dicoelia (Phyllanthaceae; Euphorbiaceae s.l.). Blumea 56: 209–213.

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Genus description

Key to the species

Species description

Dicoelia Benth.

    Dicoelia Benth., Hooker’s Icon. Pl. 13 (1879) 70, t. 1289; Pax in Engl. & Prantl, Pflanzenfam. 3, 5 (1890) 27; Merr., J. Straits Branch Roy. Asiat. Soc., Spec. no. (1921) 330; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.xv (1922) 15; in Engl. & Harms, Pflanzenfam. ed. 2, 19c (1931) 46; Croizat, J. Arnold Arb. 23 (1942) 38; Whitmore, Fl. Malay Penins. 2 (1873) 86; Airy Shaw, Kew Bull. Add. Ser. 4 (1975) 95; G.L.Webster, Taxon 24 (1975) 594; Bot. J. Linn. Soc. 94 (1987) 6; Mennega, Bot. J. Linn. Soc. 94 (1987) 122, table 2; G.L.Webster, Ann. Missouri Bot. Gard. 81 (1994) 67; Stuppy, Syst. Morph. Anat. Samen biovul. Euphorb (1995) 158, 166; Radcl.-Sm., Gen. Euphorbiacearum (2001) 124; Welzen, Blumea 56 (2011) 209; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11 (2014) 73. — Type: Dicoelia beccariana Benth.

(Shrubs to) trees, monoecious, terminal branches angular, pilose, glabrescent soon. Indumentum simple hairs. Stipules linear-triangular, caducous, apex acute, hairy on both sides. Leaves alternate, simple; petiole mainly round, basally slightly pulvinate, apically clearly pulvinate; blade elliptic to obovate, symmetric, margin entire, upper surface usually glabrous except some hairs on the basal part of the midrib, lower surface usually slightly hairy, venation raised beneath, pinnate, nerves looped and closed near the margin, veins scalariform, veinlets reticulate. Inflorescences axillary to subterminal racemiform thyrses (to pseudo-paniculate when subterminal), inserted slightly above the leaves, single per axil (to 2 together, second one much shorter), hairy, round to ribbed when dry, sexes variable, either only staminate with groups of flowers per node, pistillate with single flowers per node, or bisexual with groups of staminate and a central pistillate flower; bracts triangular, apex acute, hairy on both sides; bracteoles like bracts, but smaller; staminate flowers with even smaller subtending bracts. Flowers mainly white: pedicel round, hairy, light green; sepals 5, triangular, valvate, apex acute, hairy on both sides, white or greenish; petals 5, obovate, thick, white hairy on both sides, basal part stipe-like, patent when flowering, pinkish to distally red; disc glands indistinct, especially in staminate flowers, episepalous, small, global, hairy. Staminate flowers: petals cucullate, patent after anthesis, apex involute, hooded, grown together with the raised midrib, forming two cavities on both sides of midrib, midrib elongated as extended, free tip pointing horizontally; stamens 5, basally connate in an androphore, latter widening towards the top, hairy, filaments hairy, rose-pink, anthers elliptic, basifixed, opening introrse with lengthwise slits, both thecae separate, each in cavity of adjacent petals when young, yellow; pistillode hairy, with 5 stigmas extending above petals. Pistillate flowers: petals either straight, with an acute apex or cucullate with rounded apex; gynophore subglabrous, ovary 3- (or 4)-locular, tomentose, 2 ovules per locule, style absent or a short conical extension of the ovary, tomentose, stigmas linear, spatially separate from each other, hairy, apex widened, flat, spathulate, not split, differently coloured when dry. Fruits ovoid, not to slightly lobed, basally concave around gynophore, greyish green when young to brown, brown tomentose, dehiscing septifragally and partly loculicially from above; wall woody, thin, c. 0.8 mm thick; sepals and on Sumatra petals persistent, reflexed; columella pyramidal or slightly T-shaped. Seed ovoid, flattened-triangular on inside, smooth, often slightly notched near hilum, arilloid absent.

    Distribution — Two species, both endemic in Malesia, one found on Sumatra, the other on Borneo

    Wood — Wood shows resemblance to Cleistanthus, also part of the Phyllanthaceae (Mennega, 1987). See also Kathriarachchi et al. (2005) for information on pollen and seed anatomy.

Key to the species

1. Dicoelia beccariana Benth.

    Dicoelia beccariana Benth., Hooker’s Icon. Pl. 13 (1879) 70, t. 1289; Pax in Engl. & Prantl, Pflanzenfam. 3, 5 (1890) 27; Merr., J. Straits Branch Roy. Asiat. Soc., Spec. no. (1921) 330; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.xv (1922) 17, fig. 3; in Engl. & Harms, Pflanzenfam. ed. 2, 19c (1931) 46; Croizat, J. Arnold Arb. 23 (1942) 38; Airy Shaw, Kew Bull. 27 (1972) 3; Whitmore, Fl. Malay Penins. 2 (1873) 86; Airy Shaw, Kew Bull., Add. Ser. 4 (1975) 95; Welzen, Blumea 56 (2011) 212, Fig. 1, Map1. — Beccari PB 1397 (holo K; iso FI?, n.v.), Borneo.

    Dicoelia affinis J.J.Sm., Bull. Jard. Bot. Buitenzorg ser. 3, 1 (1920) 392, tab. 41, 42; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.xv (1922) 17. — Lectotype (designated by Welzen, 2011): Hallier 1255 (holo L; iso K, L, 2 sheets), Indonesia, Borneo, Soengei Smittouw [= Sungai Semitau]; syntype: Jaheri s.n. (L, barcode L 0146478), Indonesia, Borneo, Poeloe Madjang [= Pulau. Majang].

(Shrubs to) trees, up to 20 m high, bole up to 15 m high, dbh up to 25 cm, monoecious; flowering branches 3–5.5 mm in diameter, brown. Stipules 4–6.3 by 1.2–1.3 mm, early caducous, only protecting terminal bud. Leaves: petiole 1.7–5 cm long; blade elliptic to obovate, 11.4–46 by 4.5–14.3 cm, length/width ratio 1.9–3.7, subcoriaceous, base (somewhat rounded to) cuneate, margin flat to recurved, apex (rounded to) acuminate, upper surface dark green, glabrous except some hairs (to hirsute) on the basal part of the midrib, lower surface lighter green, slightly hairy (to hirsute on venation), venation flat to slightly sunken above, nerves 10–13 per side. Inflorescences up to 43 cm long, green to yellowish or pinkish green, per node groups of staminate flowers (or their buds or scars) and a central, single pistillate flower, sometimes only staminate flowers; bracts 1.5–2 by c. 0.5 mm. Staminate flowers 3.8–5.1 mm in diameter; pedicel 4.3–5 mm long; sepals 1–1.3 by 0.6–0.7 mm; petals 2–4 by 1.5–2.3 mm, 1–1.4 mm thick; stamens: androphore 1–2 mm high, filaments 0.8–1 mm long; pistillode consisting of 5 small, hairy globes alternating with ridges extending into 5 stigmas, latter pinkish. Pistillate flowers 5–6.3 mm in diameter; pedicel in fruit 3–8.3 mm long; sepals 1.5--3 by 0.7–1.4 mm; petals 3–4.2 by 0.7–1.1 mm, apex culculate with extended midrib, caducous, leaving thick, diamond-shaped scars; gynophore c. 1 mm high, ovary 2.5–3 by 1.7-3 mm, style absent, stigmas 2.7–6.5 mm long, greenish. Fruits 8--10 by 10–12 mm, not lobed; only sepals persistent, reflexed; columella slightly T-shaped, c. 6 mm long. Seed 6–9 by 5.3–6.4 by 5–6 mm, hilum elongate to obtriangular.

    Distribution — Malesia: Endemic on Borneo.

l= D. beccariana;«= D. sumatrana

    Habitat & Ecology — Primary lowland dipterocarp forest, riverine forest, primary kerangas forest, swamp forest seasonally inundated for at least 2–3 months, secondary forest, logged over forest; soil: Acid kaolin clay (pH 4), yellow sandy clay to leached pale yellow sand. Altitude: 10–400(–800) m. Flowering: February to November; fruiting: more or less whole year through.

    Vernacular names — Indonesian Borneo: Belet, Kemelat.

2. Dicoelia sumatrana Welzen

    Dicoelia sumatrana Welzen, Blumea 56 (2011) 212, Fig. 2, Map 1. — Type: Achmad 1281 (holo L, iso L, 2 sheets), Indonesia, Sumatra, Island Simaloer (= Pulau Simeulue).

Shrubs, monoecious, up to 1.5 m high, probably also small trees; flowering branches 3–5.5 mm in diameter. Stipules 4–9 by 1.5–1.6 mm, caducous, but present with several apical leaves. Leaves: petiole 3–5 cm long; blade 12–34 by 4.8–14.3 cm, length/width ratio 2.1–2.7, symmetric, papery to somewhat coriaceous, base cuneate, margin flat, apex acuminate, upper surface glabrous except some hairs on the basal part of the midrib, lower surface slightly hairy, venation slightly raised above, nerves 12–15 per side. Inflorescences up to 24 cm long, hairy, round, generally either staminate or pistillate, seldom both sexes together; bracts 1.8–2 by c. 0.7 mm. Staminate flowers c. 5 mm in diameter; pedicel 3.5–6 mm long; sepals 2.1–2.6 by c. 0.8 mm; petals 3–4 by 1.7–2.2 mm, c. 1.1 mm thick; stamens: androphore c. 1 mm high, filaments 0.7–1 mm long; pistillode with basal part c. 8 mm in diameter; pedicel 8.5–14 mm long; sepals 2.8–3.7 by 0.9–1.1 mm; petals 4.2–5 by 1.7–2 mm, apex acute, slightly infolded when young, straight, not infolded when in fruit; gynophore c. 1 mm high; ovary c. 3.2 by 3 mm, style generally absent, conical when present, then 0.8–1 mm long, stigmas 3–3.5 mm long. Fruits 9–11 by c. 13 mm, slightly lobed; sepals and petals persistent, reflexed, straight, not cucullate; columella pyramidal, 1–2 mm long, apically not T-shaped. Seeds 6.5–9 by 5.8–6 by 4.2–5 mm, hilum small, round. 

    Distribution — Endemic on Sumatra.

l= D. beccariana;«= D. sumatrana

   Habitat & Ecology — Soil: granitic sand. Altitude: c. 50 m. Flowering: May, August, September; fruiting: February, May.

    Vernacular names — Ketoeh hetoeh or Ketoeh hetoeh pajo (Simalur Island).