Trigonostemon longipes (Merr.) Merr.

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 199-201

15. Trigonostemon longipes (Merr.) Merr. — Fig. 7 ; Map 7

Trigonostemon longipes (Merr.) Merr. (1916b) 191; Pax & K.Hoffm. (1919) 41; Merr. (1923) 452; Airy Shaw (1983b) 47. — Dimorphocalyx longipes Merr.(1906) 82. — Lectotype (designated here): FB (Whitford) 1066 (lecto K; iso P), Philippines,Luzon, Bataan Prov., Mount Mariveles. Syntypes: FB (Borden) 1801 (BM, BO, K), Philippines, Luzon, Bataan Prov., Mount Mariveles ; FB (Merrill) 2699 (BM, K), Philippines, Luzon , Province of Rizal, Bosoboso .

Small trees, up to 4 m tall, stem c. 9 cm diam; flowering branches terete, 2–3 mm diam, glabrous except pubescent near apical buds. Bark c. 0.2 mm thick, pale brownish, smooth, wrinkled; wood pale yellowish. Stipules subulate, 0.5–1 mm long, pubescent. Leaves: petiole terete but grooved above, 1–8 cm long, glabrescent or slightly pubescent; blade oblong, sometimes oblanceolate, 5.5–16 by 2.5–6 cm, coriaceous, base cuneate, with 2 adaxial glands, 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 8–11 pairs, curved and connected along margin, veinlets reticulate, often obscure. Inflorescences often unisexual, axillary or terminal, sometimes cauliflorous, thyrsoid, up to 15 cm long, glabrous or slightly pubescent, part of staminate flowers single and cauliflorous; few glomerules on a long main rachis, each node subtended by 1 bract; latter lanceolate, up to 1.5 by 0.8 mm, often pubescent; glomerules

Map 7 Distribution of Trigonostemon longipes (Merr.) Merr. (★); T. lychnos (R.I.Milne) R.Y.Yu & Welzen (▲); T. magnificus R.I.Milne (■ including also ●); T. malaccanus Müll.Arg. (●); T. merrillii Elmer (▼).

few-flowered (often 5–10 in staminate inflorescences and 1–3 in pistillate ones), bracteate under each flower, lanceolate, up to c. 0.7 by 0.5 mm, densely pubescent. Staminate flowers c. 4 mm diam; pedicel c. 1 mm long, c. 0.45 mm diam, slightly pubescent; sepals orbicular, c. 2 by 2 mm, imbricate, base connate, apex rounded, pubescent outside; petals elliptic, c. 2 by 1 mm, contort, margin sometimes ciliate; disc lobes obovate or semi-orbicular, c. 0.5 by 0.5 mm, c. 0.15 mm thick, glabrous, apex acute; stamens 5, androphore short, often indistinct, anthers c. 0.5 mm long, gathered on the top of androphore. Pistillate flowers c. 6 mm diam; pedicel 2–3 mm long, thickened towards apex, c. 1.2 mm thick; sepals oblong, slightly accrescent in fruit, up to 3.5 by 2 mm, pubescent outside, apex rounded; petals not seen, caducous; disc lobes semi-orbicular, c. 0.5 by 1 mm, glabrous; ovary not seen. Fruits c. 1 cm diam, glabrous; wall c. 0.4 mm thick; columella c. 3 mm long. Seeds c. 6 mm diam.

Distribution — Philippines (endemic).

Habitat & Ecology — Secondary forest, on clay loam. Altitude: 175– 250 m. Flowering: January to April, September; fruiting: January, April.

Note — The altitude information is based on Merrill (1906). The ovary is probably glabrous because the fruits are glabrous. The species strongly resembles T. verticillatus var. verticillatus in the variable long petiole and the 5 stamens of the staminate flowers, but they are different in their inflorescences: several flowers (often more than 5) cluster into significant glomerules along the main rachis and the internodes are relatively distinct in T. longipes whereas in T. verticillatus var. verticillatus flowers are evenly spread along the spike-like rachis (only 1–3 flowers present per node) and the internodes are very short. A molecular phylogeny may result in a better conclusion about its distinctiveness.

Figures

Fig. 7 Trigonostemon longipes (Merr.) Merr., cultivated in Makiling Botanical Garden, University of the Philippines-Los Baños, Laguna, the Philippines. a. Top view of the tree; b. bark and a cauliflorous staminate flower; c, d. inflorescences; e. fruit. — Photos by Mark Gregory Q. Rule.