Dimorphocalyx malayanus Hook.f.

4. Dimorphocalyx malayanus Hook.f. View in CoL — Fig. 1f View Fig , Map 4

Dimorphocalyx malayanus Hook.f. (1887) View in CoL 404; Pax & K.Hoffm. (1911) 33; Merr.(1921) 346; Ridl. (1924) 266; W.L. Stern (1967) 668; Whitmore (1973) 86; Airy Shaw (1975) 96;Phattar.& Chayam.(2005) 229,f. 50. — Lectotype (designated here): Griffith KD 4785 (holo K; iso A, P), [ Malaysia,] Malacca.

Dimorphocalyx kunstleri King ex Hook.f. (1887) View in CoL 405; Pax & K.Hoffm. (1911) 32; Ridl. (1924) 266. — Type: King’s collector 1455 (holo K), [ Malaysia,] Penang.

Dimorphocalyx luzoniensis Merr. (1910) View in CoL 192; Pax & K.Hoffm. (1912) 284; Merr. (1923) 455; Whitmore (1973) 87; Airy Shaw (1975) 96; (1983) 21. — Lectotype (designated here): FB (Tamesis) 11907 (holo K;iso US), Philippines, Luzon, Prov. of Laguna, Los Baños.

Dimorphocalyx beccarii Gagnep.(1924) View in CoL 621. — Lectotype (designated here): Beccari PB 2215 (holo P; iso A, K), Borneo , Sarawak.

Trigonostemon bulusanensis Elmer (1939) View in CoL 3735; Airy Shaw (1967) 413. — Dimorphocalyx bulusanensis (Elmer) Airy Shaw (1972b) View in CoL 92; (1983) 20. — Type: Elmer 17296 (holo PNH†; iso HBG, K, L, MO, NY, S, U), Philippines, Luzon, Prov. of Sorsogon, Irosin (Mt Bulusan).

Shrubs to trees to 15 m high, dbh to 18 cm; flowering branches 2–3 mm diam, greyish brown, yellowish when dry, at most slightly striate. Indumentum mainly absent, hairs light yellow. Outer bark grey, thin, slightly roughened, not detaching; under bark usually indistinct, if distinct dark red; inner bark cream to paler red than under bark, fibrous; wood white. Stipules triangular to ovate, 1–3 by 1–3 mm, stiff, with dark brown centre and thinner, lighter brown margins, glabrous. Leaves: petiole 7–35 mm long, 0.8–1.8 mm diam, deeply furrowed above, not to slightly pulvinate basally and apically, glabrous, light green to green; blade ovate to elliptic, widest in ± middle, 2.9–19 by 0.8–10.3 cm, 1.8–3.6 times as long as wide, papyraceous (to pergamentaceous), base obtuse to cuneate to attenuate, margin entire, seldom serrulate (glandular parts extending due to revolute margin), flat to revolute, apex (acuminate to) cuspidate (to caudate), dark green above, pale green below, venation slightly raised above, raised below, secondary veins 9–17 pairs, tertiary nerves reticulate. Inflorescences axillary, short and dichasial (especially pistillate ones) to longer and thyrsoid (to slightly paniculate; especially staminate ones), staminate ones to 10 cm long, pistillate to 7 cm long, branches often flattened, glabrous, lower bracts often leaf-like, higher ones triangular to ovate, 0.7–6 by 0.3–1.5 mm, with a few hairs on the midrib outside and along the margin. Staminate flowers 6.5–13 mm diam, white; pedicel 3.7–6.5 mm long above abscission zone, round, glabrous, abscission zone basally ( Philippines, Borneo) to generally higher (SE Asia); calyx 2–5.5 mm deep, lobes triangular and indistinct in SE Asia (c. 1 by 2.5 mm) with acute to erose apices, sometimes with a subapical gland outside, ovate and distinct in Borneo and the Philippines (1.3–3.5 by 1.3–3.3 mm) with round apices without glands outside; petals elliptic to oblong, 5–7.5 by 1.8–3.8 mm, apex rounded, glabrous; disc glands obtrapezoid, 0.3–0.9 by 0.6–0.8 mm, thin, glabrous; stamens 10–12, filaments white, outer 5 (or 8) free (to seldom basally connate for c. 1 mm with androphore), filaments 2.5–5 mm long, inner 4–7 often in two layers, androphore 2.3–6 mm long, free part 1–2 mm long, anthers ellipsoid, 0.8–1.1 by 0.8– 1.5 mm, tan. Pistillate flowers 20–21.5 mm diam; pedicel 5–12 mm long above abscission zone, round, glabrous; calyx basally united, lobes ovate to oblong to obovate, 8–13 by 5–7.5 mm, apex rounded to emarginate, glabrous, usually with a gland outside just beneath apex, green to yellow; petals elliptic to obovate, c. 9.5 by 4.5 mm, apex rounded, white, glabrous; disc up to 0.4 mm high, glabrous; ovary ovoid, 2–2.2 by 1.7–2.2 mm, glabrous, smooth, bright yellow with local green tinges, style 0.8–1 mm long, cream or very pale green, stigma 2–5 mm long, basal 1–1.3 not split. Fruits 1.2–1.6 by 0.9–1 cm, smooth, glabrous, green, ripe brown; pedicel 8–19 mm long; sepals enlarging to 25 by 16 mm; wall c. 1 mm thick, exocarp detaching; columella c. 8.5 mm long. Seeds ellipsoid, 7.5–8 by 6.5–7.5 by 6–6.8 mm.

Distribution — Thailand (Peninsular), Malay Peninsula, Borneo, Philippines.

Habitat & Ecology — In primary and lowland evergreen to deciduous forest, on slopes, sandstone cliffs, among limestone outcrops. Altitude: 100– 500 m. Flowering: January to May, September; fruiting: February to June.

Note — Dimorphocalyx luzoniensis and D. bulusanensis do not differ in any characters from each other and both are also very similar to D. malayanus and, therefore, synonymised with the latter. There are some geographical differences: leaf blades are generally larger in Borneo and the Philippines ( ‘ D. luzoniensis ’, ‘ D. bulusanensis ’) than in S Thailand and Malay Peninsula (typical D. malayanus ), staminate flowers of typical D. malayanus generally have a visible abscission zone, not basal, and they are smaller with acute, very short calyx lobes (basal abscission zone and larger, with bigger, rounded calyx lobes in typical ‘ D. luzoniensis / bulusanensis ’), the pistillate sepals in S Thailand and Malay Peninsula are generally more rounded/acute and always have a subapical extrafloral nectary at the outside, while on Borneo and in the Philippines the pistillate sepals are emarginate and often lack the glands, the style and disc are more distinct in S Thailand and Malay Peninsula than in the Philippines.