Impatiens purpureoviolacea (Gilg, 1909)

Fischer, Eberhard, Abrahamczyk, Stefan, Holstein, Norbert & Janssens, Steven B., 2021, Evolution of Impatiens (Balsaminaceae) in the Albertine Rift - The endemic Impatiens purpureoviolacea complex consists of ten species, TAXON 70 (6), pp. 1273-1299 : 1281-1282

Key to the species of the Impatiens purpureoviolacea complex

1. Lower sepal and spur bucciniform, lateral united petals deep red with yellow spots, or entirely wine red...........2

1. Lower sepal navicular, abruptly constricted into a spiraled, usually filiform spur............................................3

2. Leaves herbaceous, densely hairy on both sides, lamina broadly ovate, stem densely covered with hairs, flowers with greenish bucciniform lower sepal tapering into a spur, densely hairy, spur not swollen at apex, dorsal petal deep red with greenish crest, lateral united petals deep red, yellow at throat, ovary and fruit glabrous; montane forest up to 2700 m; Democratic Republic of the Congo, Rwanda, Burundi....................................... I. gesneroidea

2. Leaves coriaceous, almost glabrous above, hairy below, lanceolate-ovate, stem densely covered with hairlike brownish scales, flowers with bucciniform wine-red lower sepal tapering into a greenish spur, swollen at apex, ± glabrous, dorsal petal wine red with greenish crest, lateral united petals uniformly wine red, ovary and fruit pubescent with tufts of white hairs; bamboo-zone, ericaceous shrub to paramo, 2500–3350 m; Democratic Republic of the Congo............................................ I. superglabra

3. Flowers magenta, lower sepal entirely greenish, ± abruptly constricted into a spiraled, broadly filiform spur, up to 2 mm in diameter, dorsal petal helmet-like, dark magenta, with green crest above ending in a long spur, not or only slightly bilobed, lateral united petals dark magenta, with dark red and yellow spots at throat; Rwanda.................................................................. I. ×troupinii

3. Flowers pink or white, lower sepal pink, whitish or greenish, navicular, with an abruptly spiraled, narrowly filiform spur, 1 mm in diameter, dorsal petal expanded, cucullate, bilobed at apex, lateral united petals pink or white ....................... 4

4. Plants densely covered with brownish hairs, stems erect, up to 60–95 (120) cm tall, flowers large, upper lateral petal 18.5–24.5 × 11–15.5 mm, purple maculae on upper lateral petals small, spot-like, ovary and fruits with brownish hair; gallery forests in grassland; Burundi......... I. urundiensis

4. Plants pubescent but not densely hairy, if densely hairy then with brownish hairs mainly on lower surface of young leaves and on stems, stems prostrate to ascending, up to 10–50 (85) cm long, flowers smaller, upper lateral petal not exceeding 7–17 × 3–9 mm, maculae large, dark pink to red with yellow ............................................................ 5

5. Ovary and fruit pilose or pubescent, plants usually densely pubescent on stems and lower surface of young leaves, base of upper lateral petal with purple or white maculae ....... 6

5. Ovary and fruit glabrous, plants usually glabrous or only with loose hairs, base of upper lateral petal with dark pink or red and yellow maculae.............................................8

6. Upper margin of the upper lateral petals straight, while lower margin on top largely overlapping with lower lateral petals; purple maculae near throat rather small, spot-like, fruit beige pubescent, leaf lamina lanceolate, margin with (25) 27–39 pairs of extrafloral nectaries, petiole with 3–7 pairs of extrafloral nectaries; montane forest; Burundi (Bururi) ..................................................... I. lutzmannii

6. Upper lateral petals curved upwards or slightly bent upwards, not largely overlapping with lower petals, purple maculae larger but sometimes ± hidden in throat, fruit beige pubescent or white pilose, lamina lanceolate or ovate, margin with 10–24 or 25–39 pairs of extrafloral nectaries, petiole with 0–2 pairs of extrafloral nectaries ................. 7

7. Fruit white pilose, purple maculae large, upper lateral petals bent or curved upwards, not largely overlapping with lower lateral petals, petal base barely yellow, upper lateral petal (7) 10–13 × 5–9 mm, leaf lamina ovate, 25– 59 × 14–36 mm, with 10–24 (28) pairs of extrafloral nectaries, apex obtuse, inflorescence with 1–2 flowers, peduncle 9–20 mm long, pedicel 7–14 mm long; montane forest; SW Rwanda (Nyungwe) ................. I. purpureoviolacea

7. Fruit beige-brownish pubescent, but purple maculae larger, upper lateral petals slightly bent upwards and not largely overlapping with lower lateral petals, upper lateral petal 11–17 × 6–9 mm, leaf lamina lanceolate, 55–90 × 22– 42 mm, with 25–39 pairs of extrafloral nectaries, apex acuminate, inflorescence with 3 flowers, peduncle (20) 30– 40 mm long, pedicel 13–22 mm long; montane forest; W of Lake Edward, NW Burundi (Kibira) ......... I. kivuensis

8. Spur 26–35 mm long, often only slightly coiled, flowers entirely white with yellow and very small spot-like purple marks on upper lateral petals, leaves, stems and flowers almost glabrous, mid-altitude forest at 1100 m, Democratic Republic of the Congo (Kahuzi-Biéga) ... I. elwiraurzulae

8. Spur 13–20 mm long, distinctly coiled, flowers pink or white with yellow and large purple marks on upper lateral petals, leaves, stems and flowers glabrous or loosely hairy; montane forest above 1700 m ......................................... 9

9. Upper lateral united petals 9–10 × 10 mm, distinctly overlapping lower lateral united petals, plants glabrous; Democratic Republic of the Congo (Kahuzi-Biéga) .... I. lotteri

9. Upper lateral united petals 10–18 × 5–7.5 mm, not overlapping lower lateral united petals, plants glabrous or loosely hairy................................................................10

10. Flowers white, occasionally single pink flowers appearing, dorsal petal divided to less than 1/3 of its length, plants densely hairy on upper leaf surface, stems and pedicels later glabrescent, leaves at margin with 10–15 pairs of extrafloral nectaries, plants often suberect; SW Rwanda..................................................... I. versicolor

10. Flowers all pink, dorsal petal divided to more than 1/3 up to 1/2 of its length, plants hairy on upper surface of young leaves, later glabrescent, leaves at margin with (16) 23–29 pairs of extrafloral nectaries, plants usually prostrate to ascending; Democratic Republic of the Congo, Rwanda.................................................................... I. ludewigii