Impatiens decurva Ruchis. & S.B.Janssens

Smets, E. F. & Janssens, S. B., 2018, Balsaminaceae of Myanmar, Blumea 63 (3), pp. 199-267 : 237

36. Impatiens decurva Ruchis. & S.B.Janssens — Map 14; Plate 3b

Impatiens decurva Ruchis. & S.B.Janssens in Ruchisansakun et al. (2018). — Type: Ruchisansakun & Makino BG Exped 734 (holo L L2071124; iso L, RAF, RANG), Myanmar, Shan State, Kalaw , N20°39'21.92" E96°34'55.89", 27 Sept. 2015 .

Lithophytic, annual herb, 6–30 cm tall. Stem erect, 1–3 mm diam, cylindrical, simple to moderately branched, red, glabrous. Leaves spirally arranged, mostly crowded towards apex of the stems. Petiole absent– 7 mm long, c. 1 mm diam, pale green to green to pink, glabrous. Lamina 10–40 by 5–15 mm, ovate to elliptic to obovate, apex acute to acuminate, base cuneate to attenuate, margin shallowly serrate, adaxial green and pilose along the leaf veins and margin, abaxial pale green and glabrous, with 3–5 long red hairs along the margin near the base; lateral veins 3–5 pairs. Flowers solitary, axillary, erect, 10–11 by 8–10 mm, 6–8 mm deep, pale pink and white, with yellow marks at the centre. Bracts <1 by <1 mm, linear to narrowly lanceolate, apex acute and mucronate, base cuneate, green with red apex, persistent. Pedicel 10–15 mm long, <1 mm diam, pale green, pilose. Lateral sepals 2, <1 by 1 mm, free, ovate to lanceolate, apex acute, base obtuse, pale green with red tip, glabrous. Lower sepal 4–5 by 2.5–3 mm, c. 2 mm deep, navicular, apex acuminate and mucronate, white with red tip, pilose outside, spurless. Dorsal petal 4–5 by 5–5.5 mm, broadly ovate, cucullate, apex round and slightly mucronate, base truncate to shallowly cordate, white, glabrous, but pilose on midrib, abaxial midvein simple or with narrow crest, c. 1 mm wide, green. Lateral united petals 7–9 mm long, free: the upper petals 4.5–5 by 2.5–3 mm, ovate, apex round, base cuneate, white to pale pink; the lower petals 6–7 by 3.5–4 mm, free, elliptic to obovate, apex unequally bilobed, pink with yellow mark at the base. Stamens: filaments c. 2.5 mm long, white to pale pink; anthers pale pink. Ovary 2 mm long, <1 mm diam, 5-carpellate, green, pilose. Fruits 8–10 mm long, 2.5–3 mm diam, fusiform, 5-lobed, green, pilose; pedicel strongly decurved from the middle in young fruiting stage. Seeds 9–11, c. 2 mm long, ovoid, brown.

Phenology — Flowering: September to October; fruiting: October.

Distribution — Endemic to Myanmar (Shan State).

Ecology — Growing on limestone at the top of montane areas in fragmented evergreen forest, 1500–1600 m altitude.

Note — Impatiens decurva is similar to I. pendula and I. muscicola but differ in having lower lateral petals with an unequally bilobed apex and a pedicel that is strongly decurved from the middle at fruiting stage.