Volume 16 > Part 1 > Year 2022 > Page 212 > Annonaceae > Monoon

13. Monoon membranifolium (J.Sinclair) B.Xue & R.M.K.Saunderswfo-0001425490

Taxon 61: 1032. 2012.— Enicosanthum membranifolium J.Sinclair, Gard. Bull. Singapore 14: 191. 1955. Fig. 43. Plate XXV: F–G.

Accepted Name : This is currently accepted.

Description : Tree up to 15 m tall, bark smooth, brown to dark brown. Twigs glabrous with conspicuous lenticels. Leaves chartaceous, slightly asymmetrically elliptic to oblanceolate, 16‒25 by 5.5‒6.5 cm, base cuneate, apex acute to acuminate, the acumen 5–10 mm long, glabrous on both surfaces, midrib grooved above, secondary veins fairly straight, 12–14 per side, tertiary venation percurrent; petioles (4‒) 5–7 mm long, grooved above. Inflorescences forming fascicles in axils of leafy and leafless twigs and also on woody tubercles of trunk, (1–)2–5-flowered, pedicels 20‒35 mm long, 0.8‒1.5 mm thick, each bearing an adnate ovate bract 3‒5 by 2.5‒3.5 mm between the base and the midpoint; buds ovoid. Sepals imbricate, free, thinly coriaceous, ovate, 5‒10(‒12) by 6‒8(‒10) mm, apex often recurved, blunt or acute, pubescent on both sides. Petals valvate from near base to the apices, erect or slightly spreading, pale green to yellowish green, coriaceous, oblong, veins conspicuous, pubescent on both sides; outer petals 30‒40(‒45) by 15‒20 mm, apex blunt to acute; inner petals 30‒45 by 12‒15 mm, base with claw 10‒12 mm long, the claws curved inward and tightly connivent over the stamens, apex free. Stamens oblong, 2–2.2 mm long, anther connective apex truncate. Carpels numerous, 2‒2.2 mm long, oblong, stigmas level with anther connective apices, capitate, 0.25–0.3 mm in diam., pubescent. Receptacle cushion-shaped with a flat apex, 4–5 mm in diam., 1–1.5 mm thick, pubescent. Fruit of up to 31 monocarps borne on a pedicel 25‒45 mm long, 3–5 mm thick. Monocarps green to pale green when mature, ellipsoid to subglobose, 1.8‒2 by 1.5‒1.8 cm, glabrous, slightly conical or rounded at apex and base, stipe (12–)15‒27 mm long, 2–3 mm thick; pericarp ca 0.5 mm thick. Seeds subglobose, 12‒14 mm in diam., brown, smooth (wrinkled when dried), often shiny.

Thailand : SOUTH-WESTERN: Kanchanaburi, Prachuap Khiri Khan; PENINSULAR: Chumphon, Phangnga, Phuket, Krabi, Trang, Songkhla, Yala, Narathiwat.

Distribution : Peninsular Malaysia (type).

Ecology : Tropical rain forests and coastal forests, sea level‒350 m alt. Flowering and fruiting: March–December.

Vernacular : Sabun nga dong (สะบันงาดง)(Kanchanaburi); sang yu (ซังหยู)(Trang); nang na dok yai (หนังหนาดอกใหญ่)(Peninsular).

Notes: Gardner et al. (2015) point out the similarity of this species to Monoon merguiense (Chatterjee) B.Xue & R.M.K.Saunders, which differs only in larger sepals and the rounded leaf base. In addition, Turner (Gard. Bull. Singapore 70: 605, 2018) reported M. nitidum (A.DC.) I.M.Turner for Thailand on the basis of specimens here regarded as M. membranifolium. The complex is in need of further study. Monoon merguiense and M. nitidum were both described from Myanmar near the Thai border.