Uganda. Western: Ruwenzori, [rec. at Kew 13 Mar 1901], W.G. Doggett s.n. (holotype: K [K000413968])

Vine or woody liana, sometimes semi-herbaceous, to 10 m. Stems flexuous, terete, glabrous to densely pubescent with mixed simple 4–6-celled and short-branched dendritic uniseriate trichomes 0.5–1(1.5) mm long, glabrescent when older; new growth almost glabrous to densely pubescent with dendritic and simple uniseriate trichomes, when these dense the new growth appearing golden in dry material. Bark of older stems reddish brown, smooth. Sympodial units plurifoliate, the leaves not geminate, evenly distributed along branches. Leaves simple, 4–12 cm long, 2–5.6 cm wide, elliptic or less commonly ovate, membraneous, the adaxial surfaces glabrous to moderately pubescent with mostly simple uniseriate trichomes 0.5–1 mm long, in more pubescent individuals some trichomes dendritic, the abaxial surfaces glabrous or with a few simple uniseriate trichomes along the veins and margins to densely pubescent with short-branched dendritic trichomes 0.5–1.5 mm long, these often drying golden; major veins 5–10 pairs, usually yellowish beneath, especially on glabrous individuals; base acute; margins entire, if the leaves otherwise glabrous the margins have a few simple trichomes to 1 mm long near the base; apex acute to acuminate; petioles 0.7–3.2 cm long, very variable in length along the stem, nearly glabrous to densely dendritic-pubescent, sometimes twining. Inflorescences terminal, 5–15(+) cm long, lax and open, many times branched, with 20–100 flowers many open at the same time, pubescence in parallel to that of stems and leaf undersides; peduncle ).5-)2–4.5 cm long, sometimes the inflorescence branches starting very near the last stem leaves; pedicels 0.8–1.2 cm long, ca. 0.5 mm in diameter at the base, ca. 1 mm in diameter at the apex, spreading at anthesis, pubescent like the rest of the inflorescence axis, but slightly less densely, articulated at the base leaving a very minute raised portion of the axis; pedicel scars irregularly spaced 1–6 mm apart. Buds ellipsoid, the corolla completely enclosed in the calyx tube until shortly before anthesis, when young the elongate sepals spreading at the bud tips. Flowers 5-merous, heterostylous, short-styled and long-styled flowers apparently borne on different plants and the plants possibly dioecious. Calyx tube 1–1.5 mm long, open-conical, the lobes 1–2 mm long, narrowly triangular with a long-acuminate tip, usually thickened and keeled abaxially (this easier to see on glabrous specimens), glabrous to densely pubescent with mixed dendritic and simple uniseriate trichomes, even if glabrous the tips with a tuft of simple uniseriate trichomes. Corolla (1.5)2–3.5 cm in diameter, pale violet or white with a darker purple centre, stellate, lobed ca. halfway to the base, the lobes 7–9 mm long, 6–8 mm wide, spreading at anthesis, variably pubescent, from almost glabrous with dense papillae on the tips and margins to densely pubescent with minute dendritic trichomes all usually < 0.5 mm long (to 1 mm long in Taylor 1408). Stamens equal; filament tube absent; free portion of the filaments 1.5–2.5 mm long, glabrous or sparsely pubsvent with dendritic trichomes (on pubescent plants); anthers 2.5–3 mm long, 1.1.5 mm wide, ellipsoid, bright yellow, connivent to somewhat spreading, smooth abaxially, somewhat sagittate at the base, poricidal at the tips, the pores lengthening to slits with age, in dry material the pores thickened and paler at the distal tips. Ovary globose, glabrous; style of different lengths on individual plants, the short-styled plants with styles 2.5–3 mm long, held within the anther cone or exceptionally to 5 mm long and at the level of the anther tips, the long-styled plants with styles 7–9 mm long, exserted 4–6 mm beyond the anther cone, glabrous (on Wollaston s.n. [SS plant from Ruwenzori] densely dendritic-pubescent in the distal half); stigma of short styles minutely capitate, of long styles strongly bilobed or clavate, the surfaces minutely papillate. Fruit a globose berry, 0.8–0.9 cm in diameter, purple when ripe, the pericarp thin and brittle in dry material, probably shiny in fresh material; fruiting pedicels 2–2.5 cm long, tapering markedly from a base ca. 1 mm in diameter to the apex 4–5 mm in diameter, the distal half usually darker in dry material, spreading, possibly somewhat woody; fruiting calyx lobes to 0.5 cm long, spreading. Seeds 10–12(16) per berry, 2.5–3.5 mm long, 2–2.5 mm wide, ovoid reniform, reddish brown, the surfaces shallowly pitted, the testal cells very small, pentagonal in outline.

(Figure 22). In the mountains of eastern Africa in Ethiopia, Kenya, Uganda, and the Democratic Republic of the Congo.

None recorded.

Montane forests, bamboo forests; often in open areas and forest edges; 1500–3700 m elevation.

(IUCN 2014).

Least Concern

Solanum runsoriense is a montane forest edge species with large, openly branching inflorescences of purple (“blue”) flowers. It is not likely to be confused with any other species on the African continent; it the only species of the ANS clade with short-styled and long-styled flowers (see below, Fig. 21). Solanum runsoriense is partly sympatric with Solanum terminale but occurs at higher elevations and apparently in wetter forests. Solanum terminale has more deeply stellate corollas, flowers tightly clustered in groups rather than evenly and widely spaced on the inflorescence branches, and bright red rather than blackish purple berries. Pubescence is extremely variable in Solanum runsoriense; populations from Ethiopia (described as Solanum benderianum) are almost completely glabrous on stems and leaves, while populations from the Ruwenzoris in Democratic Republic of the Congo and from the Aberdare Mountains in Kenya are densely pubescent with golden dendritic trichomes. Individual populations are isolated in what has been recognised as the Afromontane (Wright 1978, 1981) or Tropic-montane Flora (Linder 2014) and limited gene exchange may allow these variants to become fixed. Flower, fruit and seed morphology are constant throughout the species range.

Edmonds (2012) placed Solanum macrothyrsum in synonymy with Solanum runsoriense; she cited Dammer (1906) and Jaeger (1985) both of whom suggested there were affinities between the two taxa. The two taxa share openly branched inflorescences and Solanum macrothyrsum is superfically similar vegetatively to more glabrous forms of Solanum runsoriense, but Solanum macrothyrsum has deeply stellate corollas and anthers that open with two terminal pores that never extend to slits as the flower ages, while Solanum runsoriense has shallowly stellate corollas and anther pores that extend to longitudinal slits with age.

Solanum runsoriense has the only member of the ANS clade that is heterostylous; in all but one of the specimens we have examined flowers on a given stem are either short-styled or long-styled. The Ethiopian collection Gilbert 138 (K000788688) is the only one we have seen with fruit and short-styled flowers on same plant. No other inflorescences with short-styled flowers had fruits, and when specimens were fruiting, all flowers in the inflorescence had set fruit. Collections are often of some sheets with flowers (short-styled) and duplicates with fruit (e.g., Schimper 1227); it is not clear if these represent branches from a single plant or different individuals. Solanum runsoriense could be either monoecious or dioecious, but most monoecious solanums have a mixture of short- and long-styled flowers in the same inflorescence (Diggle and Miller 2004; Miller and Diggle 2003; Whalen and Costich 1986) so we suspect Solanum runsoriense is another instance of dioecy in the genus (see Symon 1970; Symon 1979; Anderson and Symon 1989; Knapp et al. 1998; Martine et al. 2009). Field observations on the breeding system of Solanum runsoriense are a priority, and microscopic examination of pollen morphology to see if long-styled flowers have inaperurate pollen like other dioecious solanums (e.g., Knapp et al. 1998) might help to determine the breeding system of this species.

Engler (1892) was the first to publish the name Solanum benderianum, but without description; he attributed the name to Schimper and cited Schimper’s 1863 manuscript list of plants collected in Ethiopia. Wright (1906) and Dammer (1906) both used Engler’s epithet and provided descriptions, but Wright’s treatment was published in February 1906, a few months before Dammer’s that appeared in August 1906 making Solanum benderianum Dammer an isonym and illegitimate. Both botanists attributed the name to Schimper, cited Engler’s (1892) publication and based their descriptions on two collections (presumably different duplicates), Schimper 1227 and Scott-Elliot 7733. Wright (1906) also cited Wellby s.n. from Ethiopia. Bitter (1917) later used Scott-Elliot 7733 as the type of his var. ruwenzoriense. We have lectotypified these three names with the three different specimens used in various combinations in their protologues in order to avoid making them homotypic. Edmonds (2012) incorrectly used Wright’s (1906) mis-spelling of the name “bendirianum”; we consider this a correctable spelling mistake because Wright cited Engler’s publication in which the name was spelled in the way Schimper intended, to honour his son-in-law “Herr Bender”.

De Wildeman (1922) specified no herbarium or sheet in his description of Solanum longipedicellatum (a later homonym of Solanum longipedicellatum Bitter, a synonym of the potato species Solanum stoloniferum Schltdl., Spooner et al. 2004). Of the two sheets of Bequaert 4676 at BR, we have chosen that (BR0000008993151) annotated incorrectly as “holotype” by the late R.N. Lester as the lectotype because it has a label with the number and collecting locality. The isolectotype at BR (BR0000008993120) has no original label, but has a scrawled sheet in De Wildeman’s handwriting stating the differences between his species and Solanum runsoriense.

Democratic Republic of the Congo. Nord-Kivu: Upper Ruamoli valley, 3 Aug 1952, Ross 800 (BM); Katwah Kitumo, pistes des Beulele et a Mahonge (P.N.A. [Parc Nacional Albert = Virunga]), 12 May 1948, de Wilde 55 (BR).

Ethiopia. Addis Ababa: Addis Ababa, 1956, Mooney 6712 (K). Amhara: Semien, Uulkefit, Lumalumo, 10 Jul 1909, Chiovenda 877 (FT); West Shewa region W of-Washa Forest, 3 Dec 1984, Edwards & Tewolde 3572 (ETH); Choke Mountains, Gojjam, vicinity of the upper Ghiedeb valley, 5 Aug 1957, Evans 413 (BM, ETH, FT, K); Debre Workto Mota, 30 Oct 1981, Mesfin Tadese & Kagnew 1684 (ETH, K); Mussolini Pass, between Debre Berhan and Dobre Sina, about 200 km NNE of Addis Ababa, 23 Jul 1965, de Wilde & de Wilde-Duyfjes 7369 (BR). Oromia: Menegasha State Forest, Mount Wuchacha, 48 kms due W of Addis Ababa on Ambo road, turn off just W of Menengasha village, 21 Oct 1971, Ash 1299 (EA, K); Ghidami, Mar 1939, Benedetto 390 (FT); Bale Zone, Dolo Mena (Masslo) to Goba, 29 Oct 1984, Friis et al. 3610 (ETH, K); Mount Chilalo, a few kilometres S of mountain, track leading from road South of Asella to Ticho, 25 Nov 1968, Gilbert & Gilbert 1098 (EA, K); Ticcio track; Arsi region, 28 Nov 1966, Gilbert 138 (ETH, K); Mt. Zuquala, Nov 1994, Hylander, K. 139 (ETH); Mount Maigudo, 24 Oct 1954, Mooney 6156 (EA, FT, K, S); Debre Berhan, Wofasha, 23 Mar 1955, Mooney 6475 (FT, K); ca. 10 km N of Koffale, Gobe Livestock Farm, 13 Oct 1971, Thulin 1502 (ETH, K); Mount Wuchacha, about 15 km W of Addis Ababa, 27 Oct 1965, de Wilde & de Wilde-Duyfjes 8480 (BR, ETH, K); Arsi, Mount Borulucciu, Asella to Ticcio, E slope of Mount Borulucciu, 6 Dec 1965, de Wilde et al. 9213 (BR, K). Southern Nations, Nationalities and Peoples Region: Amaro Mountains, Mount Delo, E slope, 29 Jan 1953, Gillett 15034 (K); road from Wondo to Agere Selam [Hagere Selam], 13 km from Wondo, 24 Jan 1968, Westphal & Westphal 3157 (BR); Agere Selam [Hagere Selam], about 30 km S of Wondo, 21 Oct 1965, de Wilde & de Wilde-Duyfjes 8360 (BR, ETH).

Kenya. Central: Aberdare National Park, Aberdare Mtns., ca. 1 km W of Jerusalem Gate (West), Dist. Nyandarua, 12 Jan 1975, Croat 28375 (K, MO); Katamayu, Uplands District, Aug 1933, Napier 5130 (K, MA); Murang’a, Tuso Fishing Camp, Oct 1932, Jex-Blake 3304 (EA); Aberdare National Park, North Kinangop-Nyeri road, 30 Jul 1960, Polhill 250 (BR, EA, K). Rift Valley: Samburu, Mount Nyiru, 30 Dec 1955, Adamson 543 (EA, K); Samburu, Mount Nyiru, Mbarta forest zone, 29 Mar 1995, Bytebier et al 28 (BR, EA, K); Laikipia, district around Nyasi, Lakipia Plateau and Aberdare range, 1908, Routledge s.n. (K); Naivasha, Naivasha-Nyeri track, 28 Oct 1934, Taylor 1408 (BM).

Uganda. Eastern: Mount Elgon, Apr 1930, Liebenberg 1637 (K); Mount Elgon, western section, 300 m E of Nabulalo, 1 km SE of Maika, 29 Mar 1993, Sheil & Musingizi 1813 (K); Mount Elgon, Bulambuli, 6 Sep 1932, Thanes 650 (K). Western: Ruwenzori Mountains, Kaleveru slopes, 6 kms west of Kilembe, 3 Jun 1970, Katende 345 A (EA); Mahoma, Ruwenzori Mountains 19 Jul 1960, Kendall & Richardson 25 (EA, K); Mount Ruwenzori, below Kanyasabo rock shelter, 3 Jan 1969, Lye, K. 1340 (K); Nyamitaba, R. Mobuku valley, 11 Jul 1952, Osmaston 1549 (BM); Lake Mahoma, Jul 1960, Richardson & Livingstone s.n. (DUKE); Mobuka valley, above Kichundu, 15 Jul 1952, Ross 578 (BM); Ruwenzori, Nyamgasani valley, Jan 1935, Synge 1444 (BM); Toro, Ruwenzori, Namwamba valley, 6 Jan 1935, Taylor 2913 (BM). Bwamba, Ibonde Pass, 1 Oct 1932, Thomas 767 (EA); Nyabitaba Hut, Bujuku Valley below hut, slope down to bridge, 16 Jan 1967, Wood 816 (EA); Ruwenzori E, Mt. Ruwenzori, 21 Feb 1906, Wollaston s.n. (BM).