Type:
Ecuador. Tungurahua: south of Baños, 1200-1500 m, 26 Feb 1935, Y. Mexia 6997 (holotype, US00588706 [Correll neg. 166, F-1603839, LL, NY, UC1152351]; isotype, NA0027487 [Correll neg. 165, F-1603840, LL, NY, UC1152351]).
Habit:
Herbs up to 1 m tall, semi-erect. Stems 3-7 mm in diameter at base of plant, green, usually unwinged, glabrescent to pubescent with white short hairs; tubers typically borne singly at the end of each stolon.
Sympodial structure:
Sympodial units tri- to plurifoliate, not geminate.
Leaves:
Leaves simple or odd-pinnate, the blades 16.2-33 x 9.7-23.4 cm, light green adaxially, dark green abaxially, coriaceous, densely pubescent with short white hairs, with finer and more dense hairs abaxially; lateral leaflet pairs 1-2, decreasing in size considerably toward the leaf base, with the terminal leaflet usually larger than the most distal pair of laterals; most distal lateral leaflets 5.3-13.3 x 2.4-6.3 cm, ovate to elliptic, considerably larger than the second most distal pair, the apex acute to acuminate, the base typically petiolulate and asymmetric with more tissue on the basiscopic side; terminal leaflet 9.8-17 x 6.1-9.4 cm, usually ovate, the apex acute to acuminate, the base usually attenuate; interjected leaflets 0-30, sessile, ovate to orbicular; petioles 1-6 cm, densely pubescent with short white hairs. Pseudostipules, when present 4-14 mm long, glabrescent to pubescent with white short hairs.
Inflorescences:
Inflorescences 4.5-11.5 cm, terminal with a subtending axillary bud, generally in distal half of the plant, usually forked, with 4-15 flowers, with all flowers apparently perfect, the axes usually pubescent with white short hairs; peduncle 1.5-6.5 cm long; pedicels 8-15 mm long in flower and fruit, spaced 3-5 mm apart, articulated in the middle to the proximal half.
Flowers:
Flowers homostylous, 5-merous. Calyx 7-14 mm long, the tube 4-5 mm, the lobes 2-4 mm, ovate, with linear acumens 1-2 mm long, densely pubescent with short white hairs. Corolla 2-3 cm in diameter, substellate to pentagonal, purple, the tube 1-2 mm long, the acumens 1-3 mm long, the corolla edges flat, not folded dorsally, usually glabrous adaxially, glabrescent with white short hairs abaxially, the margins of the corolla acumens densely pubescent with white short hairs. Stamens with the filaments 1-2 mm long; anthers 6-7 mm long, oblong-lanceolate, connivent, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary glabrous; style 3-10 mm x ca. 1 mm, straight, glabrous; stigma clavate to capitate.
Seeds:
Seeds from living specimens ovoid and ca. 2 mm long, whitish to greenish in fresh condition and drying brownish, with a thick covering of “hair-like” lateral walls of the testal cells that make the seeds mucilaginous when wet, green-white throughout; testal cells honeycomb-shaped when lateral walls removed by enzyme digestion.
Phenology:
Usually flowering and fruiting from January to June.
Solanum minutifoliolum is similar to S. cajamarquense of Peru; both have ovate terminal leaflets and are densely pubescent. However, S. cajamarquense has white corollas whereas S. minutifoliolum has purple to blue corollas.