Impatiens walongensis Hareesh, M.Sabu & Borah, 2017

Hareesh, Vadakkoot Sankaran, Borah, Souravjyoti & Sabu, Mamiyil, 2017, Impatiens walongensis (Balsaminaceae), a new species from North-East India, Phytotaxa 317 (3), pp. 226-230 : 226-228

Impatiens walongensis Hareesh, M.Sabu & Borah sp. nov. ( Figure 1 )

The new species resembles I. arguta J.D. Hooker & Thomson (1860:37) and I. roingensis (Hareesh et al. 2016: 187) but differs from the latter in having bulbous stem base and smaller inner lateral sepals completely enclosed by larger outer lateral sepals. It also differs from I. arguta in having ovate to obliquely-ovate smaller lateral sepals completely covered by larger lateral sepals and a broadly ovate basal lobe of the lateral united petals and from I. roingensis in having linear bracts, purplish-white or pale purple flowers, dorsal petals with sharp needle-like horns and ovate outer lateral sepals ( Table 1).

Type:— INDIA. Arunachal Pradesh: Anjaw district, Near Nangala bridge, Walong, 12 May 2016, V. S. Hareesh 143794 (holotype CAL!, isotype CALI!).

Perennial herbs up to 1 m tall, stem glabrous, nodes swollen, base bulbous. Leaves alternate or spirally arranged at the top, petiolate; lamina 4–10 × 2.5–6 cm, ovate-elliptic, acute to caudate-acuminate at apex, cuneate at base, glabrous, green to pale green above and coriaceous, pale beneath; lamina margin crenate or serrate, serration apiculate; lateral nerves 3–10 in each side, prominent; petiole up to 3–4.5 cm long, glabrous, pale green to pale pink; stipular gland small, setaceous, pink. Inflorescence axillary, pedunculate, 1–5-flowered; bract 8–9 × 1.75–2 mm, linear, acuminate at apex, glabrous, pale pink or pale green with pink streaks; peduncle 12–15 mm long, glabrous, pale pink; pedicel 2.5–3 cm long, glabrous, pale pink; lateral sepals 4, outer sepals 2, 14.5–16 × 6.5–7 mm, navicular, with deep keel, apex acuminate, glabrous, pale purplish-rose; inner sepals 2, covered by outer lateral sepals, 11–12 × 3.5–4 mm, ovate to obliquely-ovate, acuminate at apex, glabrous, pale purplish-rose; dorsal petal 17–19 × 20–21 mm, orbicular, with needle-like horn on the back, glabrous, pale purplish-rose; lateral united petals 26–28 × 14–15 mm, 2-lobed; basal lobe 11–12 × 7–8 mm, broadly ovate, apex obtuse to truncate or notched, white with pale purplish-rose shade towards apex and yellow or brownish-yellow streaks at the junction towards the centre; distal lobe 20–22 × 7–8 mm, broadly ovate, deeply notched at apex, white with pale purplish-rose shading from centre towards apex and yellow or brownish-yellow shading just below the auricle; dorsal auricle, 4.5 × 3.5 mm, rounded; lower sepal 28–30 × 16–18 mm, funnelshaped with shrunken middle part, glabrous, white externally and with yellow patch internally; spur 13–15 mm long, cylindrical, deeply curved, glabrous, pale yellowish-white with obtuse apex. Column ca. 7–8 × 2.5–3 mm, straight, curved towards the apex; filament 7–8 × 2.5 mm, glabrous, white; anther ca. 3.5–4 × 2 mm, glabrous, white. Pistil 7–8 × 1–1.5 mm; ovary ellipsoid, glabrous, pale green. Capsule 4–4.3 × 0.6–0.9 cm long, linear, glabrous, green; seeds, 3 × 2.5 mm, obovate, greenish-yellow.

Flowering and Fruiting:—May to September

Etymology:—The name denotes the type locality, i.e., Walong of Arunachal Pradesh, India.

Distribution and Ecology:— Impatiens walongensis is known to occur only from near Nangala bridge, Walong, Anjaw district of Arunachal Pradesh, northeast India. We observed more than 100 individuals along the road sides in a few localities even beyond 2 km ahead of Walong town. The species was observed in the moist open areas in association with Galinsoga parviflora Cavanilles (1796: 41 , t. 28), Strobilanthes Blume (1826: 781 , 796) sp., etc. The species was noted as being lithophytic in two localities.Apparently the new species is under serious threat of extinction due to widening of the roads, and other developmental activities which may lead to loss of its natural habitat. Based on the present knowledge and available data, conservation status is assessed as Data Deficient (DD).

Additional specimen examined (Paratype) — INDIA. Arunachal Pradesh: Upper district, 8 km towards Walong from Hawai Bridge, 10 September 2012, R. Gogoi & S. Borah 21845 (CAL).

Figures

FIGURE 1. Impatiens walongensis sp. nov. A & B. habit; C. twig with inflorescence (inset bract); D & E. flower front and top view; F. single flower showing smaller lateral sepals surrounded by larger one; G & H. dorsal petal dorsal and ventral; I & J. outer lateral sepal dorsal and ventral view; K & L. inner lateral sepal dorsal and ventral view; M & N. lateral united petal dorsal and ventral view; O & P. lower sepal ventral and side view; Q & R lower sepal inner view; S. pistil; T. column front and side view; U. capsule with seeds. Photos by V.S. Hareesh (A–G, J, K, M, Q, S, T & U) and S. Borah (H, I, L, N–P, R).