Trigonostemon bonianus Gagnep.

Yu, R. - Y. & Welzen, P. C. van, 2020, A taxonomic revision of Trigonostemon (Euphorbiaceae) outside Malesia, Blumea 65 (1), pp. 25-52 : 28-29

3. Trigonostemon bonianus Gagnep. — sect. Tylosepalum — Map 3

Trigonostemon bonianus Gagnep. (1922) 747; (1925b) 314; P.T. Li et al. (2006) 118; P.T.Li & M.G.Gilbert (2008) 274. — Lectotype (designated by Li et al. 2006): Bon 718 (P, barcode P00717086), Vietnam, Mount Trui.

Trigonostemon petelotii Merr. (1924) 425. — Type: Pételot 795 (A, barcode A00048876 ,P,barcodes P00648663 , P00648664 ,UC*,barcode UC223795 ), Vietnam, Cho-Ganh .

Trigonostemon filipes Y.T.Chang & S.L.Mo in Chang (1989) 149; H. S. Kiu (1996) 169. — Type: Longgang Exped. 12240 (holo IBK, barcode IBK00169515 ; iso MO,barcode MO934096 ), China, Guangxi, Longgang Natural Reserve .

Trigonostemon kwangsiensis Hand.-Mazz.var. viridulis H.S.Kiu in Kiu & Chen (1992) 211. — Type: Liang 66719 (holo IBSC, barcode IBSC0306903 ; iso IBK, barcodes IBK00169523 , IBK00169525 ), China, Guangxi, Longzhou, Shangjin, Longhushan .

Shrubs, 0.5–3 m tall; flowering branches 1–2 mm diam, pubes- cent when young, glabrous in old parts. Indumentum of simple hairs; translucent (oil?) dots often present in green parts. Bark c. 0.1 mm thick, white when young, dark brown to black when mature; wood pale yellow. Stipules subulate, 0.3–0.9 mm long, caducous, pubescent at base. Leaves: petiole terete but grooved above, sometimes thickened at apex and base, 0.4–4 cm long, middle part 0.6–1.1 mm diam, pubescent; blade elliptic to oblong, 5.5–16 by 1.7–6.1 cm, somewhat thin-chartaceous, base acute to rounded, 1–2 pairs of adaxial glands present, often caducous, margin distantly serrate, teeth falcate, apex acuminate to caudate, upper surface glabrous or glabrescent, lower surface sparsely pubescent; venation indistinctively triplinerved, midrib slightly raised above and distinctively elevated and pubescent beneath, secondary veins 5–8 pairs, connected along margin, tertiary veins scalariform, veinlets reticulate, sometimes obscure. Inflorescences bisexual, often terminal, paniculate thyrses, often only a few flower buds present in the inflorescences in herbarium specimens; main axis terete, 3–13 cm long, (0.2–) 0.4–0.5 mm diam, often slightly pubescent; involucral bracts as stipules; bracts linear to lanceolate to trian- gular, 0.2–3.5 by 0.2–0.6 mm, pubescent. Staminate flowers (bud) c. 2 mm diam; pedicel 0.8–3.9 mm long, 0.15–0.2 mm diam, glabrous to slightly pubescent; sepals elliptic to ovate, 0.7–1.5 by 0.3–1 mm, base connate, margin entire, apex acute, sometimes with a notch and/or an adaxial gland, pubescent outside; petals orbicular, 1.3–1.6 by 1–1.3 mm, yellow, apex rounded, glabrous; disc annular, margin undulate, c. 0.3 mm wide; stamens 3, androphore very short, indistinct, anthers globose to ellipsoid, 0.5–0.6 mm long. Pistillate flowers c. 8 mm diam; pedicel slightly thickening toward apex, 4.8–11.3 mm long, apically 0.6–0.9 mm diam when flowering, pubescent; sepals elliptic, 2–2.9 by 1–1.3 mm, apex acute, sometimes with a notch and an adaxial gland; petals as staminate flowers; disc annular, c. 0.4 mm wide, margin undulate; ovary c. 2.2 mm diam, glabrous, style c. 0.3 mm long, stigmas c. 0.5 mm long, not bifid. Fruits 0.8–1.1 cm diam, glabrous; pedicel 1.2–2.2 cm long, 1.2–1.5 mm diam (apex); sepals persistent but not accrescent; wall 0.3–0.5 mm thick, exocarp partly detaching; columella 5.7–7.7 mm long. Seeds 6.3–6.7 mm diam, marbled; hilum rhombic, 0.9–1.3 by 0.7–0.9 mm.

Distribution — China (Guangxi), Vietnam.

Habitat & Ecology — In forests, growing on limestone. Eleva- tion: 160– 650 m. Flowering: March to May,August to October; fruiting: May, August, November.

Note — The species has a unique spotting character: the inflorescences have a long (often more than 1/2 length of the whole inflorescence) and very thin peduncle without side branches.

Figures

Map 3 Distribution of Trigonostemon bonianus Gagnep.(X), T. lanceolatus (S.Moore) Pax (▲), T. pachyphyllus Airy Shaw (★) and T. tuberculatus F.Du & Ju He (●).