Trigonostemon cumingii Müll.Arg.

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 224-225

36. Trigonostemon cumingii Müll.Arg. — Map 15

Trigonostemon cumingii Müll.Arg. (1865) 213; (1866) 1107. — Tritaxis cumingii (Müll.Arg.) Benth.(1878) 221; Pax (1910) 114;Merr.(1923) 449. — Dimorphocalyx cumingii (Müll.Arg.) Airy Shaw (1969) 124; (1983b) 20. — Type: Cuming 1693 (holo P*; iso BM, E*, G*, K, L, P*), Philippines, Samar.

Shrubs, 0.3–0.5 m tall, dbh up to 4 cm; flowering branches 1–2.9 mm diam. Outer bark c. 0.1 mm thick, black to brown, smooth, puberulent when young, glabrescent; inner bark 0.1–0.2 mm thick, dark reddish; wood white to yellow. Stipules elliptic, 1.5–2 by 0.5–1 mm, appressed pubescent, caducous. Leaves: petiole terete but grooved above, 0.8–4.5 mm long, 0.9–1.1 mm diam, often more or less appressed pubescent; blade elliptic, 9–16 by 4–7.5 cm, coriaceous to chartaceous, base acute to rounded, without glands, margin crenate, teeth glandular, apex acuminate to shortly caudate, upper surface brown to black (when dry), lower surface pale brown, both sides pubescent when young, glabrous when mature; midrib flat above, elevated beneath, nerves 7–9 pairs, veins reticulate, obscure above. Inflorescences: staminate ones axillary, peduncled; peduncles sometimes short and with few branches, 0.5–1.7 cm long, 1–1.5 mm diam, appressed pubescent; bracts elliptic, 1.5–3 by 0.5–1.2 mm, margin slightly ciliate, apex acuminate, appressed pubescent outside; pistillate inflorescences not seen. Staminate flowers c. 4 mm diam; pedicel c. 0.5 mm long, c. 0.3 mm diam, pubescent to puberulent; sepals 5, elliptic, 2–2.4 by 1–1.2 mm, base connate, margin entire, apex acute to acuminate, densely pubescent to puberulent outside; petals only 3 observed, but withered, elliptic, 1.4–1.6 by 0.7–1 mm, white, base connate, margin entire, apex acute, glabrous on both sides; disc lobes irregular, nearly semi-orbicular, 0.2–0.3 by c. 0.3 mm; stamens

Map 15 Distributions of Trigonostemon angustifolius Merr. (●); T. cumingii Müll.Arg. (★); T. stenophyllus Quisumb. (■); T. whiteanus (Croizat) Airy Shaw (▲).

c. 9, arranged into 2 whorls, outer whorl 5, alternate with disc glands, opening introrse, free, filaments c. 0.15 mm long, inner whorl c. 4, opening more or less extrorse, connate into an androphore, hidden, c. 0.5 mm long, anthers ellipsoid, c. 0.6 mm long. Pistillate flowers, fruits and seeds unknown.

Distribution — Philippines (endemic).

Habitat & Ecology — Rugged country, on red clay soil. Altitude: 300 m. Flowering: June.

Note — A rare and poorly known species. The stamens are arranged into two whorls with c. 5 free outer and 4 inner connate ones, which seems typical for Dimorphocalyx , but the inflorescences are too much condensed. A molecular phylogenetic study is necessary to determine this species affiliation.