Trigonostemon longipes (Merr.) Merr.

Yu, R. - Y., Agoo, E. M. G., Callado, J. R. & Welzen, P. C. van, 2020, Taxonomic notes on Trigonostemon (Euphorbiaceae) in the Philippines, Blumea 65 (1), pp. 12-24 : 16

2. Trigonostemon longipes (Merr.) Merr. — sect. Trigonostemon — Fig. 2 ; Map 2

Trigonostemon longipes (Merr.) Merr.(1916b) 191; Pax & K.Hoffm.(1919) 41; Merr.(1923) 452; Airy Shaw (1983) 47; R.Y. Yu & Welzen (2018) 199. — Dimorphocalyx longipes Merr. (1906) 82. — Lectotype (designated by Yu & Van Welzen 2018): FB (Whitford) 1066 (K; iso P), Philippines, Luzon, Bataan Prov., Mt Mariveles.

Trees, up to 6 m tall, stem up to 12 cm diam; flowering branches terete, 1.5–6 mm diam, glabrous or pubescent. Outer bark 0.1–0.2 mm thick, reddish or pale brownish, smooth, wrinkled; inner bark 0.1–0.3 mm thick, reddish brown; wood pale yellow- ish to brown. Stipules subulate, 0.5–1 mm long, pubescent at base. Leaves: petiole terete but grooved above, 1–11.5 cm long, often slightly thickening towards apex, 0.6–1.8 mm diam (apex), often pubescent when young, glabrous when mature; blade oblong, sometimes oblanceolate, 7.5–18 by 2.5–6 cm, coria- ceous, base cuneate, with 1–2 pairs of adaxial glands, the inner pair often smaller and caducous or worn away in old leaves, margin entire or slightly crenate, apex acuminate to somewhat caudate, upper side dark green, lower side light green, both sides glabrous; midrib flat above and elevated underneath, nerves 7–11 pairs, curved and connected along margin, veinlets reticulate, often obscure. Inflorescences unisexual or bisexual, axillary or terminal, sometimes cauliflorous, thyrsoid, 3–15 cm long, 0.5–1 mm diam, glabrous or slightly pubescent, flowers often only growing in the upper half, some flowers single and cauliflorous; staminate flowers often 4–10 clustered in a glo- merule at each node, pistillate flowers often single per node, sometimes only 1 (but up to 5 in extreme cases), at the apex of the rachis; involucral bracts 2, as stipules; bracts single per node, lanceolate to oblong, 1–3.4 by 0.3–1.1 mm, often pubes- cent; flowers with a bract and up to 2 bracteoles, triangular, up to c. 1 by 0.6 mm, densely pubescent. Staminate flowers 4–4.8 mm diam; pedicel 1.5–2 mm long, 0.4–0.6 mm diam, slightly pubescent; sepals orbicular to elliptic, light green, 1.6–2.5 by 1.3–2 mm, imbricate, base connate, apex rounded, pubescent outside; petals elliptic or spathulate, 2–2.7 by 1.8–3.5 mm, dark red to purple, contorted, base cuneate, margin sometimes ciliate, apex revolute; disc lobes obovate or semi-orbicular, 0.3–0.5 by 0.3–0.5 mm, 0.1–0.15 mm thick, pink, glabrous, apex acute; stamens 5, androphore 0.8–0.9 mm long, 0.1–0.2 mm diam, filaments free part c. 0.1 mm long, anthers 0.5–0.6 mm long, yellow, apically divaricate. Pistillate flowers c. 6 mm diam; pedicel 2.5–3.5 mm long, thickened towards apex, 0.9–1.2 mm diam (top); sepals orbicular to oblong, light green- ish to pinkish, slightly accrescent in fruit, 3.5–4.5 by 2–3 mm, pubescent outside, margin ciliate, apex rounded, sometimes with an apical gland; petals caducous, oblong to spathulate, 2–3.5 by 1.8–3 mm, dark purplish, contorted, glabrous, margin entire, slightly ciliate, apex revolute; disc annular, c. 0.1 mm thick, blackish, glabrous, margin undulate; ovary green, c. 1.2 mm diam, glabrous, stigmas green, deeply bifid, arm 0.25–0.3 mm long when flowering. Fruits 0.7–1 cm diam, glabrous; wall 0.4–0.5 mm thick; columella 3.6–4.7 mm long. Seeds 4–4.5 mm diam, marbled, hilum rhombic, 0.7–1 by 0.4–0.5 mm.

Distribution — Philippines (endemic).

Habitat & Ecology — Secondary forest , on clay loam or limestone. Altitude: 200–460 m. Flowering: January to April, Sep- tember; fruiting: January and April .

Note — Measurements have been updated from the last revision ( Yu & Van Welzen 2018) and two characters are note- worthy: often 2 pairs of adaxial glands are present at the leaf base and the ovary is now certain to be glabrous. The species differs from T. victoriae in the 3 (vs 5) stamens and the non-accrescent pistillate sepals (vs much enlarged in T. victoriae ). This species is found to cohabit with ants ( Fig. 2c ; RYY and JRC, pers. obs.).

Figures

Map 2 Distribution of Trigonostemon longipes (Merr.) Merr.

Fig. 2 Trigonostemon longipes (Merr.) Merr., from Mt Daraitan,Tanay,Rizal, the Philippines.a. Flowering branch; b. inflorescence;c. infructescence,showing that the plant cohabits with ants; d. staminate flowers, top view; e. staminate flowers, lateral view; f. pistillate flower; g. pistillate flower, petals and a sepal removed, showing the blackish annular disc; h–i. fruit. — Photos by: a–c, f–g: Ren-Yong Yu; d–e, h–i: John Rey Callado.