Trigonostemon nemoralis Thwaites

Yu, R. - Y. & Welzen, P. C. van, 2020, A taxonomic revision of Trigonostemon (Euphorbiaceae) outside Malesia, Blumea 65 (1), pp. 25-52 : 40

21. Trigonostemon nemoralis Thwaites — sect. Pycnanthera — Map 5

Trigonostemon nemoralis Thwaites (1861) 277; Müll.Arg. (1866) 1108; Hook.f. (1887) 398; Trimen (1898) 51; Bourd. (1908) 504; Pax & K.Hoffm. (1911) 93; Gamble (1925) 1341; N.P.Balakr. & Chakrab. (1991) 623, f. 8; Philcox (1997) 111. — Lectotype (designated here): Thwaites CP 3570 (K, barcode K000246867; iso A*, barcode A00048874, CAL, barcodes CAL0000023670,CAL0000023671,FR*, barcode FR0036074,G-DC*,bar- codes G00319812,G00319788, GH*, barcode GH00048873,K, barcodes K000246866,K000246868,K000246869,NY*,barcode NY00273343,P,barcodes P00717116,P00717117, P00717118), Sri Lanka, Central Province, Madamahanewera.

Shrubs or small trees; flowering branches 1.5–2.6 mm diam, pubescent when young, glabrous in older parts. Outer bark c. 0.1 mm diam, pale brown; inner bark 0.1–0.2 mm thick, dark red to reddish brown; wood brown. Stipules lanceolate to linear to subulate, 1.5–4.2 by 0.2–0.8 mm, pubescent. Leaves: petiole terete but grooved above, 0.4–1.5 cm long, 0.8–2.2 mm diam, slightly pubescent; blade elliptic to oblanceolate, 6.5–19 by 1.9–5.2 cm, thick-chartaceous, base cuneately narrowed, 2 adaxial glands present, falcate, 0.7–1.2 mm long, margin distantly serrate, teeth falcate, apex acute to acuminate, gla- brescent above and glabrous beneath; venation pinnate, midrib flat or slightly raised above, elevated beneath, secondary veins 8–13 pairs, bifurcate and connected along margin, tertiary veins and veinlets reticulate. Inflorescences seemingly unisexual, axillary or terminal; staminate ones racemose thyrses; axis 5.2– 15 cm long, narrowing toward apex, basally 1.5–2 mm diam, pubescent; bracts lanceolate, 0.5–4 by 0.3–1 mm, pubescent; pistillate ones racemes, axis 3–9.5 cm long, 1.1–2.1 mm diam, pubescent, bracts triangular to lanceolate, 1.3–2.6 by 0.5–1 mm, pubescent. Staminate flowers 3.7–4.7 mm diam; pedicel 2.5–3.8 mm long, 0.15–0.2 mm diam, pubescent; sepals lan- ceolate, 1.2–1.5 by 0.7–0.8 mm, base connate, apex acute, sometimes with an indistinct apical appendage, pubescent outside; petals obovate, 1.2–2.1 by 1.1–1.4 mm; disc seemingly absent; stamens 3, sessile (filaments absent), anthers adhere to a conical mass formed by connectives, thecae ellipsoid, 0.4–0.5 mm long. Pistillate flowers (fruiting) 3.8–6.8 mm diam; pedicel 4.2–5.5 mm long, thickening toward apex, apically 0.8–1.8 mm diam; sepals lanceolate, 2–3.7 by 1–2.2 mm, pubescent, often with a protruding apical appendage outside; petals not seen, caducous; disc lobes semi-orbicular, c. 0.5 by 0.6–0.9 mm; ovary (fruiting) 3.2–4.5 mm diam, pubescent and warty, style absent, stigmas ligular, bifid, 0.8–0.9 mm long, flat at apex, 0.8–0.95 mm wide. Fruits (young) 5.4–6 mm diam, pubescent and significantly warty; sepals persistent but not accrescent; wall 5–7 mm thick, exocarp not detaching; columella 4.2–6.3 mm long. Seeds globose, 5.6–6.2 by 5.1–6 mm, marbled; hilum elliptic to heart-shaped, 1.2–1.5 by 1–1.5 mm.

Distribution — India (Travancore), Sri Lanka.

Habitat & Ecology — Flowering: February to June.

Note — The species resembles T. diplopetalus and T. longifolius , but can be distinguished from the former by the apical gland on the sepals (vs without the apical gland; but check multiple sepals) and from the latter by the sessile stamens (vs androphore c. 0.4 mm long).