Impatiens xanthina H.F.Comber

Smets, E. F. & Janssens, S. B., 2018, Balsaminaceae of Myanmar, Blumea 63 (3), pp. 199-267 : 249

53. Impatiens xanthina H.F.Comber — Map 18

Impatiens xanthina H.F. Comber (1934) 248; W.J. Kress et al. (2003) 170; Gogoi et al. (2015b) 272. — Type: Forrest 29913 (holo E E00313662), China, Yunnan.

var. xanthina

Terrestrial, annual herb, 5–23 cm tall. Stem decumbent, up to 3 mm diam, richly branched in the decumbent part, green, glabrous. Leaves spirally arranged, congested on apex. Petiole sessile– 7 mm long, glabrous to remotely pilose. Lamina 55–65 by 10–15 mm, narrowly elliptic to narrowly obovate, apex acute, base cuneate, margin serrate, adaxial green, abaxial pale green, glabrous to remotely pilose on both sides, with 1–3 pair(s) of clavate glands along the margin near lamina base, up to 2 mm long; lateral veins 8–11 pairs. Inflorescence axillary, erect, 1–3-flowered raceme. Peduncle 13–20 mm long, green, pilose. Rachis absent– 2 mm long, pilose. Flowers 10–15 mm long, 7–10 mm deep, yellow with dark brown mark at the centre. Bracts 3–4 by 1 mm, linear to lanceolate, apex acute, base cuneate, margin entire, pilose, caducous to persistent. Pedicel c. 8 mm long, <1 mm diam, densely pilose. Lateral sepals 2, 4–5 by c. 2.5 mm, free, triangular-ovate, apex acute, base truncate, green, glabrous. Lower sepal 7–8 mm long, 1.5–2 mm deep, navicular, apex acute and mucronate, yellow, glabrous, dorsal part abruptly constricted into a narrow incurved spur with spiral end, 22–25 mm long. Dorsal petal c. 6 by 4–8 mm, ovate, cucullate, apex round, base round, yellow with dark brown mark at the base, pilose along the midrib, abaxial midvein with a slight crest at the base. Lateral united petals 9–14 mm long, free: the upper petals 5–6 by 3–4 mm, elliptic, apex round, base cuneate, yellow with dark brown marks at the base; the lower petals 8–10 by 5–6 mm, free, elliptic to ovate, apex obtuse, yellow, glabrous. Stamens: filaments c. 3 mm long; anthers obtuse, yellow; pollen yellow. Ovary c. 3 mm long, c. 1 mm diam, green, glabrous. Fruits 6–10 mm long, 3–4 mm diam, fusiform, 5-lobed, green, glabrous; fruiting pedicels c. 7 mm long. Seeds unknown

Phenology — Flowering: May to December; fruiting: September to December.

Distribution — Myanmar (Kachin State), China (Yunnan Province), India (Arunachal Pradesh State).

Ecology — Growing in mossy places along streams in evergreen forest, 3000–3500 m altitude.

Other collections examined. MYANMAR, Kachin State, Kingdon­Ward 13452

(BM), Nam Tamai valley , N28° E97°40', alt. 3000–4000 ft, 10 Nov. 1937 ; Kingdon­Ward 6682 (K), Nam Tamia, alt. 3500 ft, 3 May 1926 ; Farrer 1833 ( RAF 2 sheets), Nyitadi, alt. 5000–7000 ft, 18 Aug. 1920 ; Armstrong et al. 1199 (NY2649102*), Putao district , Naungmung Township, Hkakabo Razi National Park, between Aliaung village and Ran Nam rest house, N27.7071° E98.0754°, alt. 1117 m, 1 Nov. 2015 ; Saw­Lwin KSL1052 (L, MAND, RAF), ibid.; Kingdon­Ward 20798 (BM), the north triangle, Hkinkum,alt. 3000–4000 ft, 7 May 1953 .

Note — Impatiens xanthina has small, bright yellow flowers. This colour, in combination with the arrangement in a 1–3-flowered raceme, is rather uncommon in Impatiens . Specimen Saw­Lwin 1052 (L) approaches I. xanthina var. pusilla Y.L. Chen (1978: 49) in its short stem but has larger leaves and flowers. So far, I. xanthina var. pusilla is not found in Myanmar.