Trigonostemon villosus var. merrillianus, 2018

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 220-221

d. var. merrillianus (Airy Shaw) R.Y.Yu & Welzen , comb. nov. & stat. nov. — Map 12

Trigonostemon merrillianus Airy Shaw (1971) 549, non T. borneënsis Merr. ; (1975) 203. — Dimorphocalyx (?) borneënsis Merr. (1916a) 73. — Type: Hose 420 (holo K; iso L), Sarawak, 4th Division, Baram District, Entoyut River.

Trigonostemon acuminatus Merr. (1916b) 190; Pax & K.Hoffm. (1919) 41; Merr. (1923) 451; Airy Shaw (1983b) 46. — Type: BS ( Ramos ) 24528 (holo PNH†; iso A, BM, BO, K, L, US), Philippines, Samar, Catubig River .

Trigonostemon laxiflorus Merr. (1920) 567; (1923) 451; Airy Shaw (1983b) 47. — Type: BS ( Ramos & Edaño) 31097 (holo PNH†; iso A*, K, P*, US*), Philippines.

Leaves: petioles 1–25 cm long; blade ovate to elliptic, 8–32 by 2.5–14 cm, both sides often glabrous. Inflorescences unisexual, barely branched thyrses, up to 42 cm long, often with one large and leaf-like bract under each branch; staminate flowers often cauliflorous or in densely clustered glomerulus (Borneo) or cymes ( Philippines) along a robust rachis; pistillate inflorescences racemose, robust and erect. Staminate flowers: sepals often with a faint to showy gland near the apex outside; petals sometimes with an orange to yellowish flame-like honey mark inside near the base. Pistillate flowers: sepals elliptic, entire to serrate, when serrate then teeth glandular; ovary often glabrous, occasionally slightly pubescent. Fruits pubescent.

Distribution — Borneo, Philippines.

Habitat & Ecology — Understorey in primary to burned or logged-over forests, sometimes on hill tops or slopes or along riversides, growing on red clay loam soil. Altitude: 50– 900 m. Flowering: February to June, October to December; fruiting: September to May.

Note — This variety has the most variable petioles and leaf blades and more condensed staminate flowers on inflorescences: the plants from the Philippines have relatively shorter petioles, smaller blades and less condensed staminate flowers on each inflorescence node, whereas the plants from East and West Kalimantan have longer petioles (up to 25 cm long) and larger blades; in Sarawak (type locality) and Brunei, the plants have the most condensed glomerules along the staminate inflorescences. For more details, see Fig. 18. In fact, this massive variation was also seen by Milne (1995a) when he tried to synonymise T. acuminatus , T. borneensis and T. merrillianus under T. polyanthus , although T. villosus (not T. polyanthus ) is the correct species name.