Malesian Euphorbiaceae Descriptions
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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Tapoïdes Airy Shaw, Kew Bull. 14 (1960) 473; Hooker’s Icon. Pl. 37 (1967) t. 3632; Kew Bull., Addit. Ser. 4 (1975) 200; G.L.Webster, Ann. Missouri Bot. Gard. 81 (1994) 115; Govaerts, Frodin & Radcl.-Sm., World Checkl. Bibliogr. Euphorb. 4 (2000) 1508; Radcl.-Sm., Gen. Euphorbiacearum (2001) 337; Welzen, Edinburgh J. Bot. 69 (2012) 407; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11 (2014) 185. — Type: Tapoïdes villamilii (Merr.) Airy Shaw.
Trees, dioecious; young parts hairy, soon glabrescent; latex present, colour not indicated. Indumentum of simple hairs, absent in most parts. Stipules only covering terminal bud, early caducous, scars triangular. Leaves alternate, simple, changing to smaller leaf-like bracts in the inflorescences; axillary buds apically forked; petiole long, pulvinate at both ends; blade entire, glabrous when mature, glandless, venation penninerved, raised on both sides when dry, nerves looped and closed near margin, veins and veinlets reticulate. Inflorescences difficult to distinguish but hairy axes considered as start of inflorescences, axillary to terminal, crowded near apex of twigs, a single branch to paniculate, thyrsoid, laxly many-flowered when staminate, (Radcliffe-Smith 2001): 1–3-flowered when pistillate; bracts in basal parts and at base of branches leaf-like, slightly hairy beneath, otherwise variable, with or without bracteoles. Staminate flowers actinomorphic; pedicel round, glabrous, apically widening into calyx; calyx splitting into 2 or 3 unequal parts, apically membranous and slightly bifid, venation distinct; petals 5, reflexing, white, with very distinct venation, inside lower third with multicellular simple, ferruginous patent hairs; disc ring of tightly packed lobes, latter ± trapezoid, fleshy, with long ferrugineous hairs on the top; stamens 6, in 2-series of 4+2 (Radcliffe-Smith 2001: up to 8 stamens, 5+1-3), filaments shortly connate at base, especially the inner ones, hirsute, anthers basifixed, 2-thecate, connective abaxially thickened and thus orienting thecae diagonally inward, dehiscence latero-introrse via lengthwise slits; pistillode absent. Pistillate flowers unknown. Fruits capsular, 3-lobed, 3-locular, dehiscing septicidally and loculicidally into 6 parts (Radcliffe-Smith 2001 also found three 2-valved septicidal cocci), ridged along sutures, otherwise somewhat longitudinally wrinkled when dry; pedicel long, perhaps elongated; calyx persistent, recurved, 5-lobed; disc annular, velutinous; exocarp velutinous with many short hairs and a few long ones; endocarp woody, thick; columella short, with broad, wing-like remnants of septa. Seeds (Radcliffe-Smith 2001) ovoid, ecarunculate; testa smooth, dull, dark brown.
Distribution — Monotypic genus endemic to Borneo. Placed by Airy Shaw (1967) in tribe Jatropheae, later by Webster (1994) and Radcliffe-Smith (2001) specified to subfam. Crotonoideae tribe Aleuritideae subtribe Grosserinae.
Habitat & Ecology — Primary dipterocarp forest.
Tapoïdes villamilii (Merr.) Airy Shaw, Kew Bull. 14 (1960) 474; Kew Bull. 20 (1967a) 412; Hooker’s Icon. Pl. 37 (1967b) t. 3632; W.Meijer, Bot. News Bull. Forest Dept. Sabah 7 (1967) 30; Airy Shaw, Kew Bull., Addit. Ser. 4 (1975) 200; Govaerts, Frodin & Radcl.-Sm., World Checkl. Bibliogr. Euphorb. 1 (2000) 1510, fig. p. 1511; Welzen, Edinburgh J. Bot. 69 (2012) 408, Fig. 6. — Ostodes villamilii Merr., J. Straits Branch Roy. Asiat. Soc. 76 (1917) 92; J. Straits Branch Roy. Asiat. Soc., Special Number (1921) 345. — Type: Villamil 164 (PNH, burnt; iso US?), [Malaysia, Sabah] British North Borneo, Sandakan.
Trees, up to 30 m high, bole up to 12 m, up to 20 cm dbh; flowering branches c. 4 mm in diameter, grey when dry; latex pink. Indumentum sericeous except in flowers. Outer bark smooth, greyish to spotted white; inner bark yellowish to pinkish, brittle; sapwood pale yellowish to ochre. Stipules triangular, 3–4 by 0.7–1 mm, at least hairy outside. Leaves: petiole 1–7.8 cm long, round except apical pulvinus grooved adaxially, groove closed but open near attachment, soon glabrous; blades elliptic (to somewhat obovate), 7–23 by 2.2–10.2 cm, index 2.3–3.2, symmetric, coriaceous, base broadly cuneate, apex slightly emarginate to acuminate and then mucronulate, both surfaces smooth, soon glabrous, upper slightly hairy on midrib when young, lower slightly hairy all over when young, nerves 9–11 per side. Inflorescences sericeous, up to 15 cm long, some side branches up to 12.5 cm long; bracts when leaf-like up to 5. 3 by 2.2. cm, otherwise mainly subulate, bracteoles triangular 1.5–1.8 by c. 0.8 mm, slightly hairy outside, glabrous inside. Staminate flowers c. 8 mm in diameter; pedicel c. 3.3 mm long; calyx lobes ovate, c. 3 by 2.8 mm, rather stiff; petals obovate, c. 5 by 2 mm; stamens: filaments c. 1.8 mm long, round, rather thick; anthers elliptic, c. 0.6 by 0.8 mm. Pistillate flowers unknown. Fruits c. 1.6 by 2.1 cm; pedicel up to 2.8 cm long, with abscission zone; calyx lobes somewhat variable in size, elliptic, 3–3.5 by c. 3 mm, few hairs outside, glabrous inside; style and stigma caducous; columella c. 7 mm long, septum wings c. 5 mm broad; wall c. 2.5 mm thick. Seeds not seen.
Distribution — Endemic on Borneo (Sabah & Sarawak).
Habitat & Ecology — Primary lowland dipterocarp forest on brownish soil or near mangrove; altitude: 4–70 m. Flowering: March; fruiting: March, May.
Vernacular name — Borneo, Sabah: Belit tangau (Dusun Kinabatangan).