Trigonostemon adenocalyx Gagnep.

Yu, R. - Y. & Welzen, P. C. van, 2020, A taxonomic revision of Trigonostemon (Euphorbiaceae) outside Malesia, Blumea 65 (1), pp. 25-52 : 27-28

1. Trigonostemon adenocalyx Gagnep. — sect. Tylosepalum — Map 1

Trigonostemon adenocalyx Gagnep. (1922) 747; (1925b) 319. — Type: Unknown collector ( P, barcode P00717084 ), Indochina ?

Trigonostemon lutescens Y.T.Chang & J.Y.Liang in Chang (1983) 173. — Type: Longgang Exped. 12083 (IBK, barcodes IBK00169526 , IBK00190787 ), China, Guangxi, Longgang Natural Reserve .

Shrubs, 0.4–1.2 m tall; flowering branches 1.1–3.5 mm diam, densely pubescent. Bark 0.1–0.2 mm thick, pale to dark brown; wood pale yellow. Stipules subulate, 0.4–0.7 mm long, often pubescent at base. Leaves: petiole terete but grooved above, 1–7.2 cm long, 1–2.3 mm diam, densely pubescent; blade elliptic, 9.5–28.6 by 3.5–11.7 cm, chartaceous, base acute to rounded, 2 adaxial glands present, margin distantly serrate, teeth falcate to glandular, apex acuminate, upper surface rough, with very small glandular protrusions spreading over the blade giving a sandpaper touch, both surfaces pubescent; venation triplinerved, midrib slightly raised above and elevated and pubescent beneath, secondary veins 7–12 pairs, connected along margin, tertiary veins scalariform, veinlets reticulate. Inflorescences bisexual, terminal or axillary panicles; main axis terete, 9–26 cm long, 1–1.9 mm diam, densely pubescent; bracts lanceolate to linear, 1–25 by 0.3–4 mm, pubescent. Staminate flowers 5–8.5 mm diam; buds conical; pedicel 4.7–6 mm long, 0.15–0.25 mm diam, pubescent; sepals elliptic, 1–2 by 0.5–1.4 mm, base connate, margin entire, apex acute to rounded, sometimes with a notch and an adaxial gland, slightly pubescent outside; petals flabellate, 4–7.2 by 1.7–4.5 mm, base claw-like, apex rounded, yellow to orange, glabrous; disc annular, 0.2–0.3 mm wide; stamens 3, androphore 0.9–1.7 mm long, 0.15–0.2 mm diam, free part of filaments 0.3–0.5 mm long, anthers ellipsoid, 0.5–0.6 mm long. Pistillate flowers c. 8 mm diam; buds conical; pedicel 1–1.5 cm long, 1–1.1 mm diam, pubescent; sepals lanceolate, 3–7 by 1–1.8 mm, apex acuminate; petals as staminate flowers; disc annular, c. 0.5 mm wide; ovary 0.9–1.2 mm diam, glabrous, style absent, stigmas 0.7–1.2 mm long, apically not bifid but thickened. Fruits 1.05–1.3 cm diam, glabrous, smooth, sometimes marbled; pedicel 0.8–1.7 cm long, 1.3–1.7 mm diam (apex); sepals persistent, very slightly or not accrescent; columella 4.5–6 mm long. Seeds not seen.

Distribution — China (Guangxi), Indochina (?).

Habitat & Ecology — In forests, growing on limestone. Elevation: 280– 400 m. Flowering: April to May; fruiting: April and August.

Notes — 1. The species resembles T. viridissimus (Kurz) Airy Shaw var. elegantissimus (Airy Shaw) Airy Shaw in the large paniculate inflorescences and the conical flower buds, but the leaves contain small glandular lumps on the upper surface, which give a sandpaper touch.

2. The distribution of the species in Indochina is only known from the type specimen. The collecting location of the type specimen is uncertain (marked as ‘Indo-Chine?’ on the sheet). As we doubt the presence in Indochina the species is not listed in the key to the species in Indochina .

Figures

Map 1 Distribution of Trigonostemon adenocalyx Gagnep. (●),T. capillipes (Hook.f.) Airy Shaw (X), T. capitellatus Gagnep. (★), T. heteranthus Wight (▲) and T. kerrii Craib (■).