Impatiens arguta Hook.f. & Thomson

Smets, E. F. & Janssens, S. B., 2018, Balsaminaceae of Myanmar, Blumea 63 (3), pp. 199-267 : 232-233

29. Impatiens arguta Hook.f. & Thomson — Map 12; Plate 2e

Impatiens arguta Hook.f. & Thomson (1860) 137;Hook.f. (1875) 470;(1905) 17; Collett & Hemsl.(1890) 29; Biswas (1966) 207; S. Akiyama et al. (1995) 152; W.J. Kress et al. (2003) 169; Y.L. Chen et al. (2007) 49. — Type: Hooker 101 (lecto,designated here K K000694618;isolecto B100365169,K K000694619,G G0023736*,G G00237327*,G G00237328*,G G00237929*, MPU MPU019012*,SG SG3349*), India, Sikkim,Himalaya,Darjeeling,alt. 4000–7000 ft.

Impatiens arguta Hook.f. & Thomson var. bulleyana Hook.f. (1908) t. 2875. — Type: Forrest T. 1000 (lecto, designated here K K000694030; isolecto K K000694028, K K000694029), China, Yunnan, W Yunnan wood near Chu Jung road, Sept. 1903.

Impatiens gagei Hook.f. (1911d) t. 2951. — Type: Burkill 27744 (lecto, designated here K K000694617), India, Tonglo slopes, below Simana, alt. 6000–8000 ft.

Terrestrial, perennial, glabrous herb, 50–150 cm tall, with fascicled roots. Stem 3–6 mm diam, erect, the lower portion rarely decumbent, angular, moderately branched, green to purple, glabrous. Leaves spirally arranged. Petiole 15–30 mm long, 2–3 mm diam, angular, pale green to pale pink, glabrous. Lamina 70–140 by 43–65 mm, ovate to elliptic, apex acuminate, base attenuate, margin distinctly serrate, adaxially dark green, abaxially greyish green, glabrous, with one pair of globose glands at lamina base or on leaf margin near lamina base; lateral veins 12 or 13 pairs. Inflorescence axillary, erect, 2-flowered racemes. Peduncle up to 4 mm long, c. 2 mm diam, angular, purple, glabrous. Rachis c. 2 mm long, c. 1.5 mm diam. Flowers 27–34 by 23–25 mm, c. 45 mm deep, slightly asymmetric, lilac. Pedicel 28–31 mm long, c. 1 mm diam, pinkish green, glabrous. Bracts 9–10 by c. 1 mm, linear to lanceolate, apex acute, base cuneate, margin entire, without glands, green, glabrous, persistent. Lateral sepals 4: the upper pair 6–7 by 1–1.5 mm, free, linear to narrowly ovate, apex acute and mucronate, base cuneate, pale green to deep pink, glabrous; the lower pair 10–11 by 3–5 mm, broadly obliquely lanceolate, apex acuminate, base obtuse, pale green to deep pink, glabrous. Lower sepal 18–21 by 7–10 mm, 16–25 mm deep, deeply bucciniform, apex acuminate and mucronate, lilac, distal part abruptly constricted into a strongly incurved spur, 17–20 mm long, pale green with purple dots. Dorsal petal 13–26 by 16–21 mm, ovate to broadly elliptic to orbicular to broadly obovate, cucullate to flat, apex acuminate or emarginate and mucronate, curved, base truncate to cordate, lilac, often spotted, glabrous, abaxial midvein with crescent-shaped to obtuse crest, pale to dark pink. Lateral united petals 28–32 mm long, free: the upper petals 17–20 by 6–10 mm, ovate to broadly oblong, apex emarginate and mucronate, base cuneate, lilac with pink dots near the base; the lower petals 22–25 by 7–12 mm, free, narrowly obovate, apex emarginate and mucronate, base auriculate, lilac, with yellow auricle. Stamens: filaments 5–6 mm long, white; anthers white. Ovary c. 4.5–5 mm long, c. 1 mm diam, 5-carpellate, green, glabrous. Fruits c. 25 mm long, c. 4 mm diam, cylindrical, 5-lobed, green, glabrous.

Phenology — Flowering: May to November; fruiting: July to December.

Distribution — Myanmar (Chin State, Kachin State, Shan State), Bhutan (Trashiyangtse District), China (Yunnan Province), India (Meghalaya State, Arunachal State, Sikkim State), Nepal (Dhawalagiri Zone).

Ecology — Growing in shady areas along roadsides, in mixed deciduous montane forest, 1400–2300 m altitude.

Other collections examined. INDIA, Hooker s.n. (syn M0211776,M0211777), Sikkim, Himalaya, Darjeeling , alt. 4000–7000 ft. – MYANMAR, Chin State, Mu Mu Aung et al. 092811 ( QBG), Natma Taung National Park , alt. 3070 m, N21°14.035' E93°54.039', 30 July 2013 ; Kingdon­Ward 22634 (BM), Erakan, Mt Victoria , 6000 ft, 2 Sept. 1956 ; Kachin State, Toppin 2677 (BM), NE Burmah, alt. 4500–5000 ft; Kaulback 314 (BM), Dinghputyang , N25°58' E97°53', alt. 2000 ft, 5 Aug. 1939 ; Armstrong et al. 1016 (NY2648897*), Putao district, Naungmung Township, buffer zone of Hkakabo Razi National Park , N27.6212°, E98.1682°, alt. 1590 m, 26 Oct. 2015 ; Armstrong et al. 1192A (NY2649106*), Putao district, Naungmung Township, Hkakabo Razi National Park , between Aliaung village and Ran Nam rest house, N27.7105°, E98.1024°, alt. 942 m, 1 Nov. 2015 ; Kaulback 125 (BM), Kaulback 126 (BM), Kaulback 136 (BM), Taron Valley , N28°10' E98°10', alt. 7500 ft, 19 Oct. 1938 ; Shan State, Ruchisansakun et al. 719 (L L2071089, MAND, RAF), Taunggyi, N20°46'49.61" E97°03'07.39"; Dewan Mohinder Nath Nair et al. 6375 ( RANG015305 ), Taunggyi, 6 Oct. 1963 ; Ruchisansakun et al. 722 (L L2071096, MAND, RAF), Taunggyi, N20°46'49.61" E97°03'07.39"; Ruchisansakun et al. 729 (L L2071114, MAND, RAF), Taunggyi, N20°45'33.34" E97°18'34.39"; Robertson 343 (K), Taunggyi,alt. 5000 ft; U Mg Gale­2 12162 ( RAF9663 /2), ibid., 27 Sept. 1970 .

Notes — Impatiens arguta is a widespread species, distributed from India to China, with a variable flower colour between populations.

Map 12 Distribution of Impatiens arguta Hook.f. & Thomson (●) and I. duclouxii Hook.f. (●).

Impatiens namchabarwensis R.J. Morgan et al. (2005) was mentioned as a synonym under I. arguta in the Flora of China ( Chen et al. 2007). However, I. arguta differs in having a deeply bucciniform lower sepal, which is abruptly constricted into a strongly incurved spur, while I. namchabarwensis is characterized by an infundibular lower sepal which gradually tapers into a spur. Moreover, I. namchabarwensis has a bright, ultramarine-blue colour, which is never found in I. arguta . Hooker & Thomson (1860) mentioned many specimens in the protologue but did not indicate a holotype. We select Hooker 101 (K000694618), with Hooker’s drawing and handwriting, as lectotype.

Section Scorpioidae S.X.Yu & Wei Wang in Yu et al. (2015) 13