Impatiens allanii Hook.f.

Smets, E. F. & Janssens, S. B., 2018, Balsaminaceae of Myanmar, Blumea 63 (3), pp. 199-267 : 241-242

43. Impatiens allanii Hook.f. — Map 15; Plate 3h

Impatiens allanii Hook.f. in Ridley (1914) 325; Prain (1922) t. 3038;W.J. Kress et al. (2003) 169. — Type: Allan s.n. (holo K K000694629), Myanmar, Henzada, S. Mayanaung Reserve, Kyibin Chaung.

Terrestrial, annual, glabrous herb, 37–70 cm tall. Stem erect, 3–30 mm diam, solitary or rarely branched, green to red, glabrous. Leaves decussate. Petiole 10–40 mm long, 1.5–2 mm diam, red to green, glabrous. Lamina 55–120 by 30–50 mm, ovate to elliptic to obovate, apex acute, base obtuse to cuneate to attenuate, margin shallowly crenate, adaxial green, abaxial greyish green, with many long hairs on each side of margin near the base, up to 3 mm long; lateral veins 5 or 6 pairs. Inflorescence subterminal, erect, 7–10-flowered racemes. Peduncle 58–125 mm long, 1.5–3 mm diam, red or green, glabrous. Rachis 10–30 mm long, 1–1.5 mm diam. Flowers 28–47 mm long, pink, with yellow in some parts. Pedicel 10–20 mm long, c. 1 mm diam, green or green with red base, glabrous. Bracts 4.9–10 by 2–5 mm, ovate to elliptic to obovate, apex acute to acuminate and mucronate, base obtuse, margin entire, without glands, orange to red, glabrous, persistent. Lateral sepals 2, 5–8 by 4–7 mm, free, elliptic to ovate, apex round to acute and mucronate, base obtuse, yellow or orange or green, with red dots, glabrous. Lower sepal 10–11 by 6–6.5 mm, 2–3 mm deep, navicular, apex acuminate or mucronate, curved, yellow, sometimes with a pink arrow-shaped mark near apex, distal part abruptly constricted into a long spur, 40–73 mm long, red to pale pink. Dorsal petal 8–10 by 6–12 mm, ovate to broadly lanceolate, apex acute to obtuse, base ovate, truncate, or cordate, yellow, glabrous, abaxial midvein simple to with a narrow crest. Lateral united petals 28–37 mm long, free: the upper petals 1.5–6.5 by 1–4 mm, falcate to curved ovate, apex round or acute, base stipitate, sometimes with wavy margin inside, yellow; the lower petals 24–32 by 14–20 mm, free, ovate to elliptic, apex acute to obtuse, pink with darker mark at the base. Stamens: filaments 3–4.5 mm long, yellow; anthers yellow. Ovary 3–4.5 mm long, 1–1.5 mm diam, 5-carpellate, green, glabrous. Fruits 12–15 mm long, 3–4 mm diam, fusiform, 5-lobed. Seeds c. 50, ellipsoid, c. 1 mm long.

Phenology — Flowering: July to January.

Distribution — Endemic to Myanmar (Ayeyarwady Region, Magway Region, Rakhine State).

Ecology — Growing along roadsides in open areas of evergreen forest. The species is also found near the beach, 10– 900 m altitude.

Other collections examined. MYANMAR, Magway Region, Roger 1 (K), Thayetmyo, Ale Chaung , alt. 700 ft, 28 Oct. 1911 ; Roger 2 (K), Sheolaung stream, alt. 750 ft, 3 Nov. 1911 ; Rakhine State, Ruchisansakun & Saw­Lwin 700 (L L2071055, RAF, RANG), Thoungup road, N18°39'51.5" E94°45'28.7", alt. 892 m ; Ruchisansakun & Saw­Lwin 703 (L L2071061, L L2071062, RAF, RANG), Thandwe district, Ngapali beach, N18°23'42.3" E94°20'16.8", alt. 18 m.

Note — Impatiens allanii has large, flat, bicoloured flowers with long spurs. It can grow in dry, open lowland areas but also in very humid conditions. Hence, this species is highly recom- mended for horticultural use. It is most similar to I. bracteata Colebr. ex Roxb. ( Roxburgh & Carey 1824: 459) but differs in having bracts with entire margins, instead of ciliate ones. Ridley (1914) clearly mentioned Allan s.n. (K000694629) as type in the protologue and this specimen also includes a complete illustration drawn by Hooker that is exactly the same to the specimens.