Impatiens hartnolliae Hook. f. ex Ruchis. & Suksathan, 2018

Ruchisansakun, Saroj, Suksathan, Piyakaset, Niet, Timotheüs Van Der, Smets, Erik F. & Janssens, Steven B., 2018, Three new species of Impatiens (Balsaminaceae) from Myanmar, Phytotaxa 338 (1), pp. 63-74 : 67-70

2. Impatiens hartnolliae Hook. f. ex Ruchis. & Suksathan , sp. nov. ( Figs. 4 , 5 )

Impatiens hartnolliae Hook. f. ex Ruchis. & Suksathan is most similar to I. allanii Hook. f. ( Ridley 1914: 325) but can be distinguished by its possession of a large orbicular sepal and large upper lateral petals.

Type:— MYANMAR. Rakhine State (Arakan): Akyab, Urittaung Pagoda, 5 Sep. 1907, H. S. Hartnoll s.n. (holotype K 000694663!).

Terrestrial annual herb to 36 cm tall. Stem erect, ca 12 mm in diam., richly branched, glabrous. Leaves spirally arranged. Petiole 6–12 mm long, ca. 1 mm in diam., glabrous. Lamina 110–120 × 45–50 mm, ovate to elliptic, the apex acute to acuminate, base round to obtuse to cuneate, margin crenate to serrate, adaxial surface glabrous to sparsely pilose, abaxial surface glabrous with 2–3 pairs of long hairs along the margin near base; lateral veins 8–9 pairs. Inflorescence subterminal, erect, 6–7-flowered racemes. Peduncle 10–15 mm long, ca. 1 mm in diam., glabrous. Rachis 7–14 mm long, ca. 1 mm in diam. Flowers ca. 18 mm long, ca. 15 mm wide, ca. 23 mm deep. Pedicel 9–10 mm long, ca. 1 mm in diam., glabrous. Bracts 2.5–3.5 × 1.5–2 mm, ovate, apex acute to mucronate, base round, margin entire, glabrous, persistent. Lateral sepals 2, 6.2–6.6 × 7.5–8 mm, free, orbicular to broadly elliptic, apex round to mucronate, base round, glabrous. Lower sepal ca. 10 mm long, ca. 8 mm deep, navicular, apex acuminate to mucronate, glabrous, distal part gradually tapering into a straight or curved spur, 15–17 mm long. Dorsal petal ca. 6.5 × 8 mm, broadly obovate, the apex emarginate, base obtuse, truncate, glabrous, abaxial midvein simple or with a narrow crest. Lateral united petals ca. 15.5 mm long, free: upper petals 9–10 × 5–5.5 mm, obliquely broadly oblong, apex truncate and slightly emarginate, base cuneate; the lower petals 8.5–9× 3.5–4 mm, free, oblong, apex truncate, without auricle. Stamens 5: filaments 4–5 mm long; anthers obtuse. Ovary ca. 3.5 mm long, ca. 1 mm in diam., glabrous. Fruits short fusiform, glabrous, 5-lobed. Seeds ellipsoid, ca. 1.6–2 mm long, pilose.

Phenology:— Flowering and fruiting in September.

Distribution:— Endemic to Myanmar (Rakhine state).

Ecology:— Growing in limestone soils.

Proposed IUCN conservation assessment:— Critically Endangered B1ab (i, ii, iii) + 2ab (i, ii, iii). This species is known from only one specimen from the type locality ( IUCN 2012).

Etymology:— The specific epithet is derived from the collector name, H.S. Hartnoll.

Notes:— Impatiens hartnolliae was written by J.D. Hooker on a single specimen sheet kept at Kew but was not validly published as according to Art. 30.1 ( McNeill et al. 2012). To recognize Hooker’s work on Impatiens , we used the initial name provided by him to name this new species. The species can be easily distinguished from other species in having a racemose inflorescence, truncate lateral united petals, an emarginate dorsal petal, and a fusiform fruit.

Pollination ecology: —We have not observed living plants of this species. However, based on the possession of a long, broad spur, we predict that this species is pollinated by both bees and butterflies (cf. Ruchisansakun et al. 2016).

Figures

FIGURE 4. Impatiens hartnolliae. A. Habit; B. Immature flower; C. Immature fruit; D. Ovary; E. Stamen; F. Lateral sepals; G. Lower sepals; H. Dorsal petal; I. Lateral united petals. Drawn by Saroj Ruchisansakun.

FIGURE 5. The type specimen of Impatiens hartnolliae. http://specimens.kew.org/herbarium/K001097654.