10. ASHTONIA (Phyllanthaceae)

P.C. van Welzen

Welzen, P.C. van & P.I. Forster. 2012. Five rare genera of Euphorbiaceae (sensu lato) in the Malay Archipelago: Alphandia, Ashtonia, Borneodendron, Cladogynos and Tapoïdes. Edeninburgh J. Bot. 69: 389–411.

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Genus description

Key to the species

Species descriptions

Ashtonia Airy Shaw

    Ashtonia Airy Shaw, Kew Bull. 21 (1968) 357; Whitmore, Tree Fl. Malaya 2 (1973) 62; Airy Shaw, Hooker’s Icon. Pl. 38 (1974) tab. 3702; Kew Bull., Addit. Ser. 4 (1975) 42; G.L.Webster, Ann. Missouri Bot. Gard. 81 (1994) 51; Govaerts, Frodin & Radcl.-Sm., World Checkl. Bibliogr. Euphorb. 1 (2000) 224; Radcl.-Sm., Gen. Euphorbiacearum (2001) 64; Welzen, Edinburgh J. Bot. 69 (2012) 393; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11 (2014) 86. — Type: Ashtonia excelsa Airy Shaw.

Trees, dioecious. Indumentum of simple hairs, mainly absent, only some flower parts hairy. Stipules only present around terminal bud, nearly touching, early caducous, leaving almost ring-like, blackish scars. Leaves alternate, simple, mainly terminal on branches, glabrous; petiole round except for the adaxial groove, basally and apically pulvinate, sometimes indistictly so; blade symmetric, thick coriaceous, margin entire, base and margin usually with glands adaxially, often also extrafloral nectaries abaxially near base and along the margin, apex with gland abaxially, venation slightly raised on both sides, nerves looped and connected near margin, veins and veinlets reticulate. Inflorescences axillary among and below leaves to ramiflorous, racemose thyrses, with either groups 3 to many bracteate staminate flowers or single pistillate flowers with bract and two bracteoles; bracts and bracteoles broadly ovate, apex acute. Flowers actinomorphic; sepals 4, suborbicular to broadly ovate, imbricate, margin fimbriate, hairy or glabrous; petals and disc absent. Staminate flowers small, more or less sessile; stamens 5 or 6, filaments very short, free; anthers basifixed, 2-thecate, opening latrorse with lengthwise slits; pistillode larger than stamens, hairy, monopodial triangular to square table-like structure. Pistillate flowers: ovary 3- or 4-locular, ellipsoid, glabrous, 2 ovules per locule, style present or absent, stigmas apically slightly to deeply lobed with papillae adaxially. Fruits spade-like when young to suborbicular when mature, mesocarp thick and fleshy, drying corky, during dehiscence exo- and mesocarp shed in 3 or 6 pieces, woody endocarp dehiscing partly loculicidally and septicidally and remaining attached by connection above columella, becoming flat and star-like; columella persistent, with basal thickened ring where exo- and mesocarp were attached, apically tapering. Seeds obovoid, covered by thin sarcotesta.

    Distribution — Two species, one endemic to the Malay Peninsula, the other to Borneo.

    Habitat & Ecology — In the Malay Peninsula at higher altitudes, in Borneo in primary and kerangas forest.

Key to the species

1. Ashtonia excelsa Airy Shaw

    Ashtonia excelsa Airy Shaw, Kew Bull. 21 (1968) 357; W.Meijer, Bot. Bull. Herb. Forest Dep. Sabah 10 (1968) 230; Airy Shaw, Kew Bull., Addit. Ser. 4 (1975) 42; Welzen, Edinburgh J. Bot. 69 (2012) 394, Fig. 2. — Type: S (Brunig) 4664 (holo K; iso L), Malaysia, Sarawak, Sebuyau dist., Lankan Lari.

    Blumeodendron tokbrai auct. non (Blume) Kurz: W.Meijer, Bot. Bull. Herb. Forest Dep. Sabah 10 (1968) 229, tab. opp. 64.

Trees up to 40 m high, dbh up to 40 cm; buttresses sometimes present, low, rounded, spreading up to c. 45 cm, 5–10 cm thick; flowering twigs 5–8 mm thick, often blackish. Outer bark smooth to cracked to minutely scaly, pale greyish buff to yellowish brown to reddish to light reddish-light brown, thin, soft; inner bark cream to white pinkish to orange and white mottled to pale brown, granular to fibrous, 3–10 mm thick; sapwood pale yellow to khaki to yellow-orange to light brown with red rays, medium hard. Stipules broadly ovate, 3–9 by 2.2–5 mm, apex acute. Leaves: petiole 1.8–6.2 cm long, generally distinctly pulvinate; blade elliptic, 6–18.5 by 3–10.3 cm, length/width ratio 1.8–2, base broadly (to narrowly) cuneate usually with 2 or more large extrafloral nectaries on the abaxial surface, usually absent along the margin or only in the lower half of the blade, margin recurved, with no glands to a few in lower half, apex emarginate to broadly acute, usually damaged in specimens seen, upper surface medium green, glossy, usually drying dirty greenish yellow, lower surface pale green, drying brownish, nerves 8 or 9 per side. Inflorescences up to 8.5 cm long; bracts up to 2.4 by 2.5 mm. Flowers green. Staminate flowers seen in bud: sepals c. 1.1 by 0.9 mm, hairy outside; stamens glabrous; pistillode hairy. Pistillate flowers: pedicel c. 1 mm long, round; sepals c. 1.3 by 1.3 mm, glabrous; ovary c. 2 by 1.5 mm; style 0.8–1 mm, stigmas 1.3–2 mm long, split in upper 2/3. Fruits 1.8–3.6 cm in diameter when dry, up to 5.1 cm when fresh, yellowish to orange to reddish, acidic; pedicel up to 2 cm long; exo- and mesocarp 3–5 mm thick when dry; column 22–27 mm long. Seeds 3–6, 9–10 by 5–5.3 mm; sarcotesta red.

    Distribution — Endemic to Borneo.

    Habitat & Ecology — Primary lowland mixed dipterocarp forest (sometimes co-dominant), secondary forest, riparian forest, transition heath forest to mixed dipterocarp forest, kerangas/heath forest (Tristania – Dacryodes, very mossy), peat swamp forest (Shorea albida – Dryobalanops rappa association); soils: sand to white kerangas sand. On heath forest smaller than in primary forest. Altitude: 10–1250 m. Flowering: January, April, May; fruiting: March to December. The plant probably accumulates heavy metals and, therefore, colours dirty greenish yellow when dry.

    Uses — Fruit edible (Kirkup 768).

    Vernacular names — Kalimantan Timur: Arang arang; Poeah koekang; Renseng renseng; Sarawak: Buah belabol (Kelabit); Senumpul; Tampoi.

    Notes — 1. S (Chai) 35801 and S (Awa) 51080 have smaller fruits and a thinner exo- and mesocarp, but are otherwise not different.

2. Teijsmann HB 8712 & Teijsmann HB 8648, both sterile, from Kalimantan, have narrower leaves with a narrowly cuneate base that lacks the very obvious hollow glands. Instead they have smaller glands and the upper surface is more shiny when dry. However, stipules, colour of the dried leaves, etc. are the same. Endert 3694 and Hallier 2274 (also from Kalimantan) form intermetiates with the normal type of leaves.

2. Ashtonia praeterita Airy Shaw

    Ashtonia praeterita Airy Shaw, Kew Bull. 27 (1972) 4; Whitmore, Tree Fl. Malaya 2 (1973) 62, Fig. 1; Airy Shaw, Hooker’s Icon. Pl. 38 (1974) tab. 3702; Airy Shaw, Kew Bull., Addit. Ser. 4 (1975) 42; Govaerts, Frodin & Radcl.-Sm., World Checkl. Bibliogr. Euphorb. 1 (2000) 224, fig. p. 225; Welzen, Edinburgh J. Bot. 69 (2012) 395, Fig. 3. — Type: Soepadmo 783 (holo K), Malaysia, Pahang-Selangor border, Gunong Bunga Buah.

Emergent trees, up to 30 m high, up to 48 cm diam.; bole fluted to 2 m; crown dense, rounded, domed with short massive branches; flowering twigs 4–5 mm diam. Outer bark grey to brown, narrowly closely fissured ridges, very rough with squarish chunky scales; inner bark cream to cream fawn to flecked orange, firm, fibrous; sapwood cream with fawn flecks, hard. Stipules broadly ovate 5–5.5 by 2–2.3 mm. Leaves: petiole 0.7–4.4 cm long, hardly to distinctly pulvinate; blade elliptic, 2.3–8.5 by 1.2–4.7 cm, length/width ratio 1.7–1.8, base broadly cuneate to cuneate, abaxial basal extra floral nectaries usually not distinct, margin often recurved, with regular glands, sometimes with extrafloral nectaries in the basal half abaxially near the margin, less often also near apex, apex emarginate to rounded, drying brownish, wilting leaves yellow; venation c. 6-nerves per side. Inflorescences up to 6 cm long; bracts up to 2.5 by 2.1 mm. Staminate flowers not seen, description after Airy Shaw (1974): staminate sepals c. 1 mm long, glabrous, filaments c. 1 mm long, pistillode c. 1 by 0.5 mm. Pistillate flowers (partly after Airy Shaw 1974): pedicel c. 2 mm from abscission zone; sepals 1.8–2 by c. 1.5 mm, not persistent; ovary c. 2 by 1 mm; style absent, stigmas c. 1.2 mm long, slightly apically split. Fruits only seen unripe, 1.4–1.5 by c. 1.4 cm when dry, shiny, deep red; exo- and mesocarp up to 2.2 mm thick when dry. Seeds not seen.

    Distribution — Endemic in Peninsular Malaysia.

    Habitat & Ecology — Found at higher altitudes, c. 1300 m. Flowering: March; fruiting: May, June.