Impatiens siangensis Gogoi, 2015

Gogoi, Rajib & Borah, Souravjyoti, 2015, Impatiens siangensis (Balsaminaceae), a new species from Arunachal Pradesh, India, Phytotaxa 192 (2), pp. 117-120 : 117-119

Impatiens siangensis Gogoi sp. nov. ( Figure 1 )

Differs from I. marianae Hooker (1905:27) by the absence of white blotches on the upper leaf surface, flower only partially purple, bract ovate, glabrous, lateral sepals glabrous, dorsal petal glabrous, navicular, lower sepal navicular with straight purple streaks and spur almost straight. From I. porrecta Wallich (1832:7275) , it differs in having stem, leaves, and floral parts glabrous, stem branched, flower partially purple, lower sepal navicular with straight purple streaks and spur almost straight.

Type: — INDIA. Arunachal Pradesh: East Siang , between Pasighat and Along, 95°3’26.56”E, 28°07’44.29”N, 18 July 2013, R. Gogoi 30501 (holotype CAL!; isotypes ARUN!, ASSAM!) .

Annual erect to prostrate, succulent herbs, sparsely branched, to 25 cm tall. Stem green or pinkish, terete, nodes not swollen. Leaves confined to upper portion of the stem, alternate, petiole 0.7–4.5 cm long, pinkish, with few filiform glands, stipule absent; blade simple, elliptic to broadly elliptic, 1.5–7 × 1–4.5 cm, glabrous, vein pairs 7–8, opposite, base cuneate, apex acute, margin crenate, bristle present terminal on the teeth. Inflorescence axillary, single flowered, peduncle 1.5–2 cm long, greenish-purplish, bud pinkish, spur prominently curved in bud;flower only partially purple with darker spots or stripes, pedicel to 1.5 cm long, pink-purplish, bract at the base of the pedicel, persistent, green, ovate, 0.3 × 0.2 cm, apex acute, mid vein inconspicuous, glabrous. Flower: lateral sepals 2, ovate to obliquely ovate, 0.6–0.8 × 0.5–0.6 cm, greenish white, flushed with pink, apex acute, margins entire, transparent, membranous; lower sepal navicular, purplish, with straight purple streaks, tapering into a spur, to 5 mm deep, mouth to 8 mm wide, beaked, beak to 1 mm, spur yellowish white, often purple tinged or striped, to 2.3 cm long, linear, straight to slightly bending inward, tip white; dorsal petal purple, cucullate, obovate, to 1.2 × 0.6 cm, apex emarginate, dorsal side slightly raised; lateral united petals purple, bilobed, unequal, without blotches, to 1.5 × 1 cm (whole), basal lobe unevenly triangular, to 0.8 × 0.7 cm, clawed, claw to 3 mm long, apex acute to obtuse, distal lobe to 1 × 0.7 cm, dolabriform, apex obtuse, dorsal auricle golden yellow, triangular, entire, 1 mm across; stamen to 6 mm, not upright, horizontal, anther lobes obtuse. Capsule short, elliptic to ovate lanceolate, turgid at middle, green, glabrous, to 1.3 cm long, 4–5 mm in width; seeds obovate, 1.5 × 1 mm, green, papillate.

Phenology:—Flowering and fruiting in the rainy season, June-September.

Distribution and habitat:— Impatiens siangensis is endemic to the Siang Valley of Arunachal Pradesh. This species is quite common in moist areas near streams and shady forest margins at 300–600 m elevation. The new species was seen growing in association with species such as Impatiens prostrata Hooker (1905:31) , Alocasia fornicata (Roxb.) Schott (1854:410) , Colocasia esculanta (L.) Schott (1832:18), Hedychium stenopetalum Lodd. (1833:1902) in tropical forest margins.

Etymology:—The specific epithet refers to “the Siang Valley”, where from it was collected.

Conservation status:—Presently Impatiens siangensis is not threatened in its natural habitat, hence its conservation status is Least Concern (LC), according the IUCN Red List criteria ( IUCN 2010).

Figures

FIGURE 1. Impatiens siangensis: A. Habit; B. Lateral view of flower; C. Frontal view of flower; D–E. Different views of bracts; F. lateral sepals (dorsal view); G. dorsal petal (ventral view); H. dorsal petal (dorsal view); I. lateral united petals (ventral view); J. lateral united petals (dorsal view); K. lower sepal with spur; L. stamens; M. capsule; N. seeds. Photo of A & B taken in between Pasighat and Along by Rajib Gogoi.