Trigonostemon inopinatus Airy Shaw, 1976

Yu, R. - Y. & Welzen, P. C. van, 2020, A taxonomic revision of Trigonostemon (Euphorbiaceae) outside Malesia, Blumea 65 (1), pp. 25-52 : 35-36

12. Trigonostemon inopinatus Airy Shaw — sect. Spinipollen — Map 4

Trigonostemon inopinatus Airy Shaw (1976) 396; (1980) 691. — Type: Webb & Tracey 7762 (holo BRI, barcode BRI-AQ0205473, on 2 sheets), Australia, Queensland, Cawley State Forest, west of Cathu between Mackay & Proserpine .

Small trees or shrubs, up to 7 m tall; flowering branches 1.1–2.2 mm diam, pubescent when young, glabrous in old parts. Outer bark c. 0.1 mm thick, pale brown to grey; inner bark c. 0.1 mm thick, reddish brown; wood pale yellowish. Stipules subulate, 0.1–0.35 mm long, sometimes pubescent at base. Leaves: petiole terete, grooved above, 1–2.2 cm long, 0.8–1.7 mm diam, sometimes very slightly thickened towards base and apex, pubescent; blade elliptic, 5–10 by 2.4–4.8 cm, chartaceous, base acute, 2 adaxial glands present, margin distantly serrate, apex acute to acuminate, upper surface pubescent when young, glabrescent, lower surface often pubescent; venation pinnate, midrib flat above and elevated beneath, pubescent beneath, secondary veins 4–8 pairs, curved and connected along margin, tertiary veins reticulate, often obscure. Inflorescences bisexual, axillary; staminate ones thyrsoid, dichotomously branching, often subtended by bracts and supported by a peduncle, peduncle terete, 0.8–4.5 cm long, 0.4–1 mm diam, pubescent, bracts oblong, 2.8–25 by 1–6 mm, pubescent on both sides; pistillate inflorescences cymes, peduncle terete, 1.2–2.5 cm long, 0.5–1 mm diam, bracts oblong to lanceolate, 7–16 by 2–3.8 mm, pubescent on both sides. Staminate flowers c. 6 mm diam; pedicel thickening toward apex, 4.2–6 mm long, apically 0.4–0.6 mm diam, pubescent; sepals elliptic to lanceolate, 1.8–2.7 by 0.7–0.8 mm, base connate, margin entire, apex acuminate, pubescent outside; petals obovate to flabel- late, 3–3.5 by 2.1–2.2 mm, yellow or cream, glabrous, with a reddish honey mark near base, apex rounded; disc glands 5, 0.5–0.6 by 0.2–0.3 mm; stamens 3, androphore c. 1.3 mm long, c. 0.4 mm diam, anthers ellipsoid, 0.7–0.8 mm long. Pistillate flowers c. 7.5 mm diam; pedicel thickening toward apex, 9.5–13 mm long and apically 1–1.2 mm diam when flowering, elongating to 1.7–2.3 cm long and apically 1.5–1.7 mm diam in fruit, pubescent; sepals lanceolate, 4–7.5 by 1.2–2.2 mm when flowering, enlarged up to 18 by 6.7 mm when fruiting, green, pubescent on both sides, base connate, margin entire, apex acuminate; petals as in staminate flowers, but larger and caducous, 4–5 by 3.5–4.8 mm; disc annular, 5-notched, membranous; ovary c. 1.6 mm diam, pubescent; style absent; stigmas 0.9–1 mm long, in middle c. 0.5 mm diam, adaxially grooved, apically thickened and horseshoe-like, 0.8–0.9 mm diam. Fruits sparsely pubescent; sepals persistent; wall 0.4–0.5 mm thick, exocarp partly detaching; columella 5.5–6.5 mm long. Seeds 6.7–7 mm diam, brown; hilum round, 1.7–1.8 by 1–1.5 mm.

Distribution — Australia (Queensland, endemic).

Habitat & Ecology — Notophyll Vine forests, on granite, near streams. Elevation: 140– 820 m. Flowering: May to July; fruiting: February and July.

Note — See note under T. montanus R.Y.Yu & Welzen. The short and dichotomously branching staminate inflorescences are typical for the species.

Figures

Map 4 Distribution of Trigonostemon cherrieri Veillon (■) and T. inopinatus Airy Shaw (▲).