Impatiens tanintharyiensis Ruchis.,Suksathan & Saw-Lwin

Smets, E. F. & Janssens, S. B., 2018, Balsaminaceae of Myanmar, Blumea 63 (3), pp. 199-267 : 219

9. Impatiens tanintharyiensis Ruchis.,Suksathan & Saw-Lwin — Map 5; Plate 1g

Impatiens tanintharyiensis Ruchis.,Suksathan & Saw-Lwin in Ruchisansakun et al. (2017) 171. — Type: Ruchisansakun & Thet Yu Nwe 707 (holo L L2071066;iso L, RAF, RANG), Myanmar, Tanintharyi Region, Dawei, Thet Kal Kwet Village, Hawang falls , alt. c. 146 m, 17 Aug. 2015.

Lithophytic, annual, glabrous herb, 15–25 cm tall. Stem erect, cylindrical with small ridges near the nodes, 3–7 mm diam, unbranched to sparsely branched, upper part slightly zigzag, not swollen at nodes, red to purple with dark purple dots. Leaves spirally arranged, adaxial green, abaxial pale green. Petiole 10–30 mm long, 1–1.5 mm diam, green to red with dark red dots. Lamina 40–65 by 15–25 mm, elliptic to ovate to lanceolate, apex acute, base obtuse to attenuate, margin shallowly serrate; lateral veins 4 or 5 pairs; extrafloral nectaries present as a stalked short gland on each side of the margin at the base. Inflorescence axillary, 1-flowered, erect. Flowers 35–42 by 22–26 mm, 28–32 mm deep, highly asymmetric, pink with white centre and a pair of yellow marks on base of the lower lateral petals. Bracts c. 2 by 1 mm, narrowly triangular, apex acute, green. Pedicel 20–30 mm long, c. 1 mm diam, pink with red dots. Lateral sepals 2, 5–7 by 5–6 mm, ovate to broadly ovate, sometimes slightly oblique, apex acute to acuminate and mucronate, base obtuse to cordate, pink with green tips. Lower sepal 13–16 by 8–10 mm, 14–15 mm deep, deeply bucciniform, pink outside and whitish inside with pink veins and a yellow mark, distal part gradually constricted into a curved spur, 19–22 mm long, pink with deep pink dots, blunt. Dorsal petal 12–13 by 15–17 mm, broadly ovate to broadly elliptic to broadly obovate, flat, recurved near the base, pink with a green tip, curved backward, apex cordate and mucronate, base cuneate, abaxial midvein with a narrow crescent-shaped crest near the base, c. 1 mm wide. Lateral united petals connate: the upper petals 12–15 by 18–22 mm, broadly obovate, apex truncate, pink with white base; the lower petals 23–30 by 9–13 mm, connate, obovate, apex round to shallowly bilobed, pink with white base and yellow mark at the base. Stamens: filaments c. 4 mm long, white; anthers white. Ovary 4 mm long, 1 mm diam, 4-carpellate, green, glabrous. Fruits 15–17 mm long, c. 3 mm diam, clavate, 4-lobed, 14–16-seeded. Seeds c. 2.5 by 1 mm, brown.

Phenology — Flowering:August to September; fruiting: September.

Distribution — Endemic to southern Myanmar (Tanintharyi Region).

Ecology — Growing on decaying organic material that is present on granular metamorphic rock of granitic schist facies, shady or open sunny areas along a waterfall, 140–160 m altitude.

Other collections examined. MYANMAR, Tanintharyi Region, Ruchisansakun & Thet Yu Nwe 708 (L L2071069, RAF, RANG), Dawei, Thet Kal Kwet Village, Rachaung falls , N14°24'38.08" E98°11'10.43", alt. 155 m, growing on rocks in shady areas along a waterfall, 17 Aug. 2015 .

Note — Impatiens tanintharyiensis is closely related to I. spectabilis , I. psittacina and I. cardiophylla Hook.f. (1909: 14) although it is morphologically quite distinct ( Ruchisansakun et al. 2017). The species differs from I. spectabilis in having asymmetric flowers and a longer spur. Further details on the differences between I. tanintharyiensis and its close allies are provided in Ruchisansakun et al. (2017).

Section Impatiens in S.X.Yu et al. (2015) 191