Solanum phoxocarpum
Citation:
Syst. Bot. 35: 903. 2010.
Type:
KENYA. Masai: Narok District, Lake Naivasha to the Enesambulai Valley, on the crest of the Western Rift Wall, 2 Nov 1969, P. G. Greenway & Kanuri 13869 (holotype: EA! [no barcode]; isotype: K! [K000441270]).
Last edited by:
Sandra Knapp (May 2014)
Written by:
Maria S. Vorontsova & Sandra Knapp
Habit:
Erect shrub to small tree, 1-6 m, prickly or unarmed. Young stems terete, densely stellate-pubescent and prickly or unarmed, with multangulate sessile trichomes, the rays 11-16, 0.1-0.2 mm long, the midpoints same length as the rays or up to 0.8 mm long, the prickles 6-15 mm long, 2-7 mm wide at base, straight to curved, conical to flattened, orange-brown, glabrous to sparsely stellate-pubescent in the lower half, spaced 20-200 mm apart; bark of older stems glabrous to glabrescent in patches, red-brown to almost white.
Sympodial structure:
Sympodial units plurifoliate.
Leaves:
Leaves simple, the blades 6-8 cm long, 2.5-4 cm wide, ca. 2.5 times longer than wide, elliptic, chartaceous, drying strongly discolorous; adaxial surface reddish-green, glabrescent; abaxial surface white-gray, densely stellate-pubescent, with porrect and multangulate, sessile or stalked trichomes, the stalks ca. 0.1(-0.2) mm long, the rays 11-16, 0.15-0.3 mm long, the midpoints same length as the rays or to 0.8 mm long, with 0(-2) prickles on both surfaces; the primary veins (4-)5-6 pairs, the tertiary venation visible on both surfaces; base cuneate; margins subentire to weakly lobed, the lobes 1-2(-3) on each side, up to 0.5(-1.5) cm long, extending to 1/3 of the distance to the midvein, broad-deltate, apically rounded; apex acute; petiole 0.5-0.9 cm long, less than 1/6 of the leaf blade length, moderately to densely stellate-pubescent, unarmed.
Inflorescences:
Inflorescences apparently terminal or lateral, 3-5.5 cm long, unbranched, with 1-7 flowers, 1(-5) flowers open at any one time, densely stellate-pubescent, unarmed; peduncle 0-6 mm long; pedicels 1.8-3 cm long in long-styled flowers, 0.8-1.2 cm long in short-styled flowers, erect, articulated at the base, moderately stellate-pubescent, with 0-2 prickles on long-styled flowers, unarmed on short-styled flowers; pedicel scars spaced 1-2 mm apart.
Flowers:
Flowers 5(-6)-merous, heterostylous and the plants andromonoecious, with the lowermost 1-3 flowers long-styled and hermaphrodite, the distal flowers short-styled and staminate. Calyx ca. 15 mm long in long-styled flowers, ca. 7 mm long in short-styled flowers, densely stellate-pubescent, with 0-15 prickles, the lobes 7-10 mm long in long-styled flowers, ca. 4 mm long in short-styled flowers, narrow-deltate, apically acute to apiculate. Corolla ca. 3 cm in diameter in long-styled flowers, ca. 1.7 cm in diameter in short-styled flowers, mauve, stellate, lobed for 1/2-2/3 of the way to the base, the lobes 10-15 mm long, 4-5 mm wide in long-styled flowers, 6 mm long and 3-4 mm wide in short-styled flowers, deltate, spreading or somewhat reflexed, densely stellate-pubescent abaxially, the trichomes porrect, sessile, the rays 8-15, 0.1-0.3 mm long, the midpoints shorter than the rays. Stamens equal, with the filament tube ca. 2 mm long, the free portion of the filaments ca. 1.2 mm long; anthers 3.5-4 mm long, connivent, tapering, poricidal at the tips. Ovary densely stellate-pubescent in the upper 1/5; style ca. 0.7 cm long in long-styled flowers, stout, almost straight, stellate-pubescent in the lower 1/3.
Fruits:
Fruit an ellipsoid berry, ca. two times longer than wide, apically pointed, retaining the same shape throughout development, 1-3(-5) per infructescence, 2.8-3.7 cm long, 1.8-2.2 cm wide, the pericarp smooth, sometimes warty, evenly green when young, yellow at maturity, glabrous; fruiting pedicels 2.5-4 cm long, 1.2-1.8 mm in diameter at base, woody, pendulous, with 2-10 prickles; fruiting calyx lobes elongating to ca. 25 mm long, 1/6-1/4(-1/2) the length of the mature fruit, sometimes reflexed, with 0-15 prickles.
Seeds:
Seeds ca. 30 per berry, 4-4.5 mm long, 3-4 mm wide, flattened-reniform, brown.
Chromosome number:
Not known
Distribution:
Kenya and Tanzania; woodland, damp forest understory or secondary scrub; 2100-3000 m elevation.
Phenology:
Flowering and fruiting throughout the year.
Phylogeny:
Solanum phoxocarpum is a member of the Old World clade of the spiny solanums (Leptostemonum), and within that group it belongs to a strongly supported Aculeastrum Clade along with Solanum aculeastrum and Solanum thomsonii (Vorontsova et al. 2013).
References:
Levin, R. A., N. R. Myers, and L. Bohs. 2006. Phylogenetic relationships among the “spiny solanums” (Solanum subgenus Leptostemonum, Solanaceae). Amer. J. Bot. 93: 157-169.
Vorontsova, M. S., S. Stern, L. Bohs, and S. Knapp. 2013. African spiny Solanum (subgenus Leptostemonum, Solanaceae): a thorny phylogenetic tangle. Bot. J. Linn. Soc. 173: 176-193. doi:10.1111/boj.12053
Common names and uses:
Local Names. Kenya: Osigawai, Sigawet (Masai language).
Uses. Fruits used medicinally; plants used as hedges.
Solanum phoxocarpum is sympatric with the closely related S. aculeastrum, and can be distinguished by the unusual cylindrical pointed fruits, subentire leaves on fertile branches, and mauve flowers; the two species frequently grow together in woodland above 2100 m. Solanum aculeastrum has more deeply lobed leaves and abundant prickles, while S. phoxocarpum has entire leaves and fewer prickles.
Udo Dammer also recognized the distinctness of these plants and annotated the sheet Scheffler 306 (K) as “Solanum sepiaceum Dammer var. fructile verrucans spec. nov.” in his handwriting, with a printed label “Brit. Uganda. Station Lamuru. Buschiges Hochland. b.c. 3000 m”. This name does not seem to have been published and the specimen is not cited in the protologue of S. sepiaceum. “Station Lamuru” most likely refers to Limuru in central Kenya.