Trigonostemon xyphophylloides (Croizat) L.K.Dai & T.L.Wu

Yu, R. - Y. & Welzen, P. C. van, 2020, A taxonomic revision of Trigonostemon (Euphorbiaceae) outside Malesia, Blumea 65 (1), pp. 25-52 : 45-46

31. Trigonostemon xyphophylloides (Croizat) L.K.Dai & T.L.Wu — sect. Tylosepalum — Fig. 4 ; Map 8

Trigonostemon xyphophylloides (Croizat) L.K.Dai & T.L.Wu in Chun et al. (1963) 277;H.S. Kiu (1996) 163;P.T.Li & M.G.Gilbert (2008) 273. — Cleidion xyphophylloides Croizat (1940) 503. — Type: Wang 34005 [cited as ‘34006’ in Croizat 1940, probably a typo; marked as holotype in A by Croizat] (A*, barcode A0004596, IBK, barcode IBK00169539, IBSC, K, barcode K000959334), China, Hainan, Ya County.

Small trees, 1.5–3 m tall; flowering branches c. 3.5 mm thick, often glabrous. Bark 0.3–0.5 mm diam, dark brown to grey, sap reddish black when solidified; wood pale brown, pith sometimes hollow. Stipules subulate, 1.9–2.4 mm long, light green, gla- brous or sometimes pubescent at base. Leaves: petiole 0.5–3 cm long, slightly grooved above, more or less pubescent; blade oblanceolate, lower part cuneately narrowed, 22–49 by 5.4–11 cm, coriaceous, base round to truncate, adaxially 2 stipellae present, subulate to falcate to linear, 1.9–2.2 by 0.3–0.6 mm, yellow to light green, blade margin distantly serrate, teeth glandular, apex acuminate or sometimes rounded, green above, light green beneath, glabrous on both surfaces; venation pin- nate, midrib slightly raised above, distinctly elevated beneath, secondary veins 13–18 pairs, slightly curved, bifurcate and connected near margin, tertiary veins reticulate. Inflorescences unisexual; staminate ones cauliflorous, short and condensed cymes or thyrses, bracts semi-orbicular to lanceolate, 0.3–1.8 by 0.3–1.5 mm, pubescent; pistillate ones terminal or axillary, often racemose, axis 1.5–2.4 cm long, pubescent, bracts lan- ceolate, 1.3–2.4 by 0.8–1 mm, pubescent. Staminate flowers 3.1–4 mm diam; pedicel 3.1–6 mm long, 0.1–0.2 mm diam, pinkish, glabrous; sepals ovate to elliptic, 1–1.2 by 0.7–1 mm, imbricate, pinkish green, base connate, apex often rounded, more or less pubescent outside, sometimes with an apical gland outside; petals oblong to oblanceolate, 1.5–5.3 by 0.5–1.3 mm, orange with a reddish honey mark at base, visible on both sides, apex acute, glabrous on both sides; disc glands rectangular to trapezoid, 0.25–0.35 by 0.25–0.4 mm, somewhat fleshy, apex truncate to rounded; stamens 3, androphore erect, 0.2–0.3 mm long, c. 0.3 mm diam, anthers free, divaricate, thecae 0.4–0.5 mm long, connective with an apical appendage. Pistillate flowers (bud) at least 2 mm diam; pedicel c. 3 mm long, c. 0.5 mm diam, pubescent; sepals ovate to triangular, c. 1 by 0.9 mm, pubescent; petals, disc and ovary not seen. Fruits green, glabrous; pedicel 0.8–1 cm long, c. 2.8 mm diam; sepals persistent, slightly accrescent, c. 2 by 1.2 mm; columella 6.5–8 mm long. Seeds globose or ellipsoid, 0.85–0.9 by 0.7–0.85 mm, dark orange to brown when dry.

Distribution — China (Hainan, endemic?).

Habitat & Ecology — Understorey in forests. Flowering: July; fruiting: April, July, September to October.

Note — The species is both morphologically and phyloge- netically (Yu et al. 2019) close to T. aurantiacus , but the leaves are much larger and lighter in colour.

Figures

Map 8 Distribution of Trigonostemon fragilis (Gagnep.) Airy Shaw (●), T. lii Y.T.Chang (★), T. murtonii Craib (▲), T. villosus Hook.f. var. nicobaricus (Chakrab.) N.P. Balakr. & Chakrab. (■) and T. xyphophylloides (Croizat) L.K.Dai & T.L.Wu (X).

Fig. 4 Trigonostemon xyphophylloides (Croizat) L.K.Dai & T.L.Wu, cultivated in South China Botanical Garden. a. Growing habit; b. leaf base, showing stipel- lae; c. branch tip, showing stipules; d. bark; e. branch, showing ramiflorous inflorescences; f. top view of staminate flower; g. flower buds and lateral view of staminate flowers; h. columella of fruit. — Photos by Ren-Yong Yu.