Impatiens lobbiana Turcz.

Smets, E. F. & Janssens, S. B., 2018, Balsaminaceae of Myanmar, Blumea 63 (3), pp. 199-267 : 216-217

6. Impatiens lobbiana Turcz. — Map 5; Plate 1e

Impatiens lobbiana Turcz. (1859) 270. — Type: Lobb 384 (lecto,designated here KW KW001000647*; isolecto K K000694801), Myanmar (Burma), Moulmein, 1846.

Lithophytic, annual, glabrous herb, 30–60 cm tall. Stem erect, the lower part sometimes decumbent, 4–7 mm diam, moderately or richly branched, green with red dots. Leaves spirally arranged. Petiole 15–60 mm long, 2–2.5 mm diam, cylindrical, green with red dots adaxially. Lamina 85–130 by 35–50 mm, ovate, apex acuminate, base attenuate, margin crenate, adaxial green, abaxial greyish green, with one pair of cylindrical glands near the lamina base; lateral veins 6 or 7 pairs. Flowers solitary, axillary, (18–)26–45 by (19–)28–45(–50) mm, (20–)30–40(–42) mm deep, pink. Pedicel cylindrical, 45– 60 mm long, 1–1.5 mm diam, green. Bracts 4–7 by 1.5–3 mm, oblanceolate, apex acute, base cuneate, margin entire, green, persistent. Lateral sepals 2, 5–8 by 4–7 mm, free, ovate, apex acuminate, base obtuse, green. Lower sepal 11–15 by 5–5.5– 7 mm, 3–7 mm deep, navicular, apex acute and mucronate, base obtuse, pale green, distal part abruptly constricted into a narrow straight to curved spur, 30–45 mm long, green. Dorsal petal 7–22 by 7–25 mm, obovate, strongly reflected, flat, apex obcordate and mucronate, base cuneate, pink, abaxial midvein with a crescent-shaped crest at the base. Lateral united petals 17–32 mm long, connate: the upper pair 10–25 by 7–21 mm, broadly oblong to obovate, apex obcordate and cuspidate, base stipitate, pink with white mark at the base (yellow when dry); the lower pair 15–27 by 6–15 mm, connate, oblong to obovate, apex shallowly emarginate and cuspidate, base without auricle, pink with white mark at the base (yellow in dried specimens), sometimes with a red line around the white mark. Stamens: filaments 2–4 mm long, pale green; anthers white. Ovary 2–4 mm long, 1–1.5 mm diam, 4-carpellate, green. Fruits c. 13 mm long, 4 mm diam, clavate, 4-lobed, green. Seeds 20–24, ellipsoid, c. 2 mm long, brown.

Phenology — Flowering:August to October; fruiting:August to December.

Distribution — Endemic to southern Myanmar (Kayin State, Mon State).

Ecology — Growing on limestone in shady or open areas in the mixed deciduous forest, 30–70 m altitude.

Other collections examined. MYANMAR, Mon State, Ruchisansakun & Thet Yu Nwe 711 (L L2071071, RAF, RANG), Mawlamyine, Himeinkanein , N16°19'19.43" E97°42'34.06", 19 Aug. 2015 ; Ruchisansakun & Thet Yu Nwe 712 (L L2071074, RAF, RANG), Mawlamyine, Himeinkanein , N16°19'02.07" E97°42'19.07", 20 Aug. 2015 ; Ruchisansakun & Thet Yu Nwe 713 (L L2071075, RAF, RANG), Mawlamyine, Kalagon , N16°32'00.29" 97°42'53.85", 20 Aug. 2015 ; Ruchisansakun & Thet Yu Nwe 741 (L L2071147), Mawlamyine , N16°22'48.6" E97°45'45.4 '; Kayin State, Ruchisansakun & Thet Yu Nwe 716 (L L2071080, RAF, RANG), Hpa-An, Zwegabin Mountain , N16°49'41.99" E97°40'28.74", 20 Aug. 2015 ; Ruchisansakun & Thet Yu Nwe 743 (L L2071149), Hpa-An, Sadan cave , N16°44'21.7" E97°43'00.2", 18 Oct. 2015 ; Ruchisansakun & Thet Yu Nwe 746 (L), Hpa-An, Zwegabin mountain , 18 Oct. 2015 ; Ruchisansakun & Thet Yu Nwe 748 (L L2071159), Hpa-An, 20 Oct. 2015.

Map 5 Distribution of Impatiens lobbiana Turcz. (●), I. micromeris Hook.f. (●), I. psittacina Hook.f. (●) and I. tanintharyiensis Ruchis., Suksathan & Saw-Lwin (●).

Notes — Impatiens lobbiana is highly variable in flower size between populations. The populations we observed in Mawlamyine have much smaller flowers than those from Hpa-An (18–26 mm vs 40–45 mm). This species is similar to I. spectabilis Triboun & Suksathan ( Suksathan & Triboun 2009: 176) from Thailand but differs in having an obcordate apex on the upper lateral petals, instead of a truncate to obtuse apex. Turczaninow (1859) cited the specimen Lobb 184 in the protologue, but Lobb 184 (K000858226) is Henckelia marginata (C.B.Clarke) A.Weber from Peninsular Malaysia. However, we believe that Lobb 384 (KW001000647) – deposited in the National Herbarium of Ukraine (KW) – was the specimen Turczaninow was referring to, although Singapore is written on the label. However, a duplicate at Kew (K000694801) was collected in Moulmein (Moolmein), Myanmar, and Lobb 380­385 is also from Myanmar. As we cannot confirm with certainty that the specimen Lobb 384 (KW001000647) is a holotype, we designate it as lectotype, because it best matches the protologue.