Impatiens prainii Hook.f.

Smets, E. F. & Janssens, S. B., 2018, Balsaminaceae of Myanmar, Blumea 63 (3), pp. 199-267 : 226-227

18. Impatiens prainii Hook.f. — Fig. 14; Map 9

Impatiens prainii Hook.f. (1905) 14; (1911d) t. 2959; S. Akiyama (2017) 314. — Type: Prain 377 (lecto,designated in Akiyama (2017) K K000694764; isolecto K sheet 1 with illustration, K sheet 2), India, eastern Himalaya, Sikkim, Lachung Valley, near Choongtang.

Herb, 10–40 cm tall. Stem up to 3.5 mm diam, erect to decumbent, moderately branched, glabrous. Leaves spirally arranged, crowded towards apex of the stem. Petiole absent– 2 mm long, glabrous. Lamina 25–50 by 6.5–11 mm, narrowly elliptic to lanceolate, apex acute to acuminate, base cuneate, margin crenate-serrate to deeply crenate with small teeth, coriaceous, adaxial deep green and glabrous, abaxial purple and remotely pilose, one pair of stipular glands at petiole base; lateral veins 5–7 on each side of midrib. Inflorescence axillary, erect, (1–)2(–4)-flowered raceme. Peduncle 6.5–12 mm long, glabrous. Rachis 3–5 by 1–1.5 mm, ovate to lanceolate, apex acuminate or aristate, base obtuse, margin entire, glabrous. Flowers 12–18 mm long, 16–23 mm deep, asymmetric, purple. Bracts 3–5 by 1–1.5 mm, ovate to lanceolate, apex acuminate or aristate, base obtuse, margin entire, glabrous, persistent. Pedicel 9–20 mm long, c. 1 mm diam, glabrous. Lateral sepals 2, 3.5–4.5 by 2–2.5 mm, free, obliquely ovate, apex acuminate to aristate, base obtuse to cordate, purple, glabrous. Lower sepal 8.5–9.5 by 4–4.5 mm, 5–6 mm deep, deeply navicular, apex acuminate and aristate, c. 2 mm long, purple, glabrous, distal part gradually narrowed into a straight to upcurved spur, incurved in young flowers, 12–14 mm long. Dorsal petal 8.5–10 by 7–8 mm, ovate to orbicular, cucullate, apex obtuse and mucronate, base obtuse to truncate, purple, glabrous, abaxial midvein with a narrow crest. Lateral united petals 25–50 mm long, free: the upper petals 8.5–9 by 4–5.5 mm, ovate to obovate, apex obtuse, base cuneate, purple with white base; the lower petals 18–25 by 4–5 mm, free, narrowly ovate to narrowly elliptic to oblong, apex acute, base without auricle. Stamens: filaments 3–3.5 mm long. Ovary c. 3 mm long, glabrous. Fruits 17–25 mm long, c. 2 mm diam, linear, glabrous.

Phenology — Flowering: July to September; fruiting:August to September.

Distribution — Myanmar (Kachin State), Bhutan (Miongar District), India (Sikkim State), Nepal (Sankhuwasabha District).

Ecology — Growing on wet rocks in shady areas in evergreen forest, 2500–3400 m altitude. Despite its relatively wide distribution, this species is rare in Myanmar.

Other collections examined. MYANMAR, Kachin State, Kingdon­Ward 12976 ( BM,K), Mungku Hkyet , N27°45' E97°50', alt. 8000–9000 ft (2440–2740 m), 19 Aug. 1937 .

Note — Impatiens prainii is closely related to I. holocentra but differs in having narrower leaves.