Trigonostemon polyanthus Merr.

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 207-209

23. Trigonostemon polyanthus Merr. — Map 8

Trigonostemon polyanthu s Merr. (1914) 492; (1923) 452; Airy Shaw (1983b) 48. — Type: BS ( Ramos ) 1645 (holo PNH †; iso BM, BO, BRI *, G *, GH *, L, NY *, P *, SING), Philippines, Samar, Cauayan Valley .

Trigonostemon diffusus Merr. subsp. condensus R.I. Milne (1995a) 47. — Type: PNH ( Lagrimas et al.) 39433 (holo K; iso L, PNH†), Philippines, Luzon, Camarines Norte Province, Ilyang Binuauangan .

Shrubs, 2–3 m tall; flowering branches terete, 1.5–3 mm diam, slightly pubescent when young. Outer bark c. 0.1 mm thick, pale greyish, smooth; inner bark c. 0.1 mm thick, reddish brown; wood pale red or yellow. Stipules subulate or falcate, 0.5–1 mm long, pubescent. Leaves: petiole 0.8–3.2 cm long, pubescent, sometimes thickened at apex and base; blade elliptic, 4–15 by 2–4.5 cm, membranous or chartaceous, base truncate to rounded to acute, often with 2 adaxial falcate glands, margin entire or slightly distantly serrate, apex acuminate, upper surface glabrous, lower surface glabrescent to scattered pubescent; venation penninerved, slightly pubescent on lower side, midrib slightly raised above and elevated beneath, nerves 5–9 pairs, bow-shaped, connected along margin, veins and veinlets reticulate, often obscure. Inflorescences axillary, staminate ones paniculate thyrses, pubescent, main rachis up to 10 cm long, along secondary rachises (or tertiary rachises) scorpioid cymes, paintbrush-like and many-flowered, bracts linear to triangular, 0.5–5 by 0.2–0.5 mm, pubescent outside; pistillate inflorescences cymose, 1- or few-flowered near apex and with few depauperate flowers below, peduncles c. 3 cm long, pubescent, bracts as staminate ones. Staminate flowers c. 4 mm diam; pedicel 2.5–3.5 mm long, c. 0.2 mm thick, pubescent; sepals elliptic, 1.2–1.6 by 0.3–0.6 mm, pubescent outside, margin sometimes slightly ciliate, apex acute to rounded; petals obovate to spathulate, 2.5–3 by 1–1.3 mm, base cuneate, margin entire, apex rounded, dark purplish and with one yellow or red flame-like honey mark in the lower middle part, glabrous, smooth; disc lobes oblong to trapezoid, c. 0.3 by 0.2 mm, c. 0.1 mm thick, apex acute or obtuse, glabrous; stamens 3, androphore erect, c. 0.5 mm long, anthers clustered at top of androphore, ellipsoid, c. 0.5 mm long, connectives apically with numerous droplets (or expanded cells) with secretion. Pistillate flowers c. 5.5 mm diam; pedicel slightly thickened towards apex, c. 4 mm long, apically c. 0.7 mm diam, sericeous; sepals oblong or lanceolate, 3.5–4.5 by 1–1.2 mm, margin sometimes with a few teeth, apex acute to acuminate, sericeous outside, often sparsely sericeous inside; petals as staminate flowers but larger, 4–4.5 by 1.5–2.7 mm; disc lobes semi-orbicular, c. 0.5 by 0.5 mm, apex rounded to acute; ovary c. 0.9 mm diam, densely pubescent, styles indistinct, stigmas c. 0.7 mm long, deeply bifid into 2 arms, each arm c. 0.55 mm long, thickened abaxially, base horseshoe-shaped. Fruits and seeds not seen.

Distribution — Philippines (Samar and Luzon).

Habitat & Ecology — Flowering: April to June.

Notes — 1. A distinct species with paintbrush-like staminate inflorescences. Only 2 specimens present, the type specimen from Samar and PHN ( M. Lagrimas et al.) 39433 from Luzon .

2. Milne (1995a) wrongly cited PNH ( Ramos ) 42686 as type of T. polyanthus (but later corrected this in an erratum via a printed sheet among the specimens), as it is not the type and actually belongs to T. villosus . Therefore, the reference of Milne (1995a) is not listed under T. polyanthus .

3. The holotype for T. diffusus subsp. condensus cited by Milne (1995a), PHN (M. Lagrimas et al.) 39437, might be a misprint as it should be PHN (M. Lagrimas et al.) 39433 (same date and place as 39437). He also cited BS ( Ramos ) 1645 as a paratype, but he probably did not notice that it was the type of an older name – T. polyanthus . Although T. diffusus shares some similarity with T. polyanthus in the inflorescences, the differences are also striking and necessitate that both species are kept distinct, e.g., the inflorescences of T. diffusus are more elongated, diffuse and paniculate with a relative clear main rachis in the middle (PNH (M. Lagrimas et al.) 56725) and much longer internodes, and the pedicels are glabrous and thinner. Both species are relatively rare, more collections are desired.