Citation:
Tent. Fl. Abyss. 2: 106. 1850.
Type:
ETHIOPIA. Choa, R. Quartin-Dillon & A. Petit s. n. (lectotype, designated by Lester 1997: P! [P00343690]; isolectotypes: P! [P00343691, P00343692, P00343693]).
Last edited by:
Sandra Knapp (May 2014)
Written by:
Maria S. Vorontsova & Sandra Knapp
Habit:
Erect or procumbent shrub, 0.7-2 m, densely prickly. Young stems terete, sparsely to moderately stellate-pubescent and densely prickly, with porrect sessile trichomes, the rays 6-8, 0.15-0.3 mm long, the midpoints 0.2-1.5 mm long, the prickles 8-16 mm long, 1.5-6 mm wide at base, straight, narrow-deltate, flattened, yellow-orange, glabrous or sparsely pubescent in the lower ¼, spaced 1-10 mm apart; bark of older stems glabrescent to moderately stellate-pubescent, orange-brown.
Sympodial structure:
Sympodial units plurifoliate.
Leaves:
Leaves simple, the blades 1.7-6 cm long, 0.8-3 cm wide, 2-3.5 times longer than wide, elliptic, chartaceous, drying concolorous to discolorous, orange-brown; adaxial surface glabrescent, the trichomes with midpoints 0.7-1.5 mm long; abaxial surface sparsely to moderately stellate-pubescent, with porrect, sessile trichomes, the rays (5-)6-8, 0.3-0.5 mm long, the midpoints 0.7-1.5 mm long, with 1-5 prickles on both surfaces; the primary veins 2-3(-4) pairs, the tertiary venation usually not visible to the naked eye; base cuneate to acuminate; margins entire or lobed, the lobes 1-3 on each side, up to 0.5 cm long, extending to 2/3 of the distance to the midvein, broad-deltate to oblong, apically rounded; apex acute, sometimes obtuse; petiole 0.1-0.4(-1.5) cm long, 1/10-1/5 of the leaf blade length, moderately stellate-pubescent, with 0(-1) prickles.
Inflorescences:
Inflorescences apparently lateral, 1.5-2.5 cm long, unbranched, with 3-5 flowers, 1-3 flowers open at any one time, moderately stellate-pubescent, unarmed; peduncle less than 2 mm long; pedicels 0.7-1.3 cm long, recurved, articulated at the base, moderately stellate-pubescent, with 0-5 prickles; pedicel scars spaced 1-4 mm apart.
Flowers:
Flowers 5-merous, apparently all perfect. Calyx 7-12 mm long, moderately stellate-pubescent, with 0-15 prickles, the lobes 4-6 mm long, deltate, apically acute to acuminate. Corolla 1.5-2.3 cm in diameter, white to pale mauve, sometimes with purple midveins, stellate, lobed for ca. 4/5 of the way to the base, the lobes 6-10 mm long, 1.8-3 mm wide, narrow-deltate to narrow-ovate, spreading, moderately stellate-pubescent abaxially, the trichomes porrect, sessile, the rays 6-8, 0.1-0.3 mm long, the midpoints 0.5-1.5 mm long. Stamens equal, with the filament tube 1-1.5 mm long, the free portion of the filaments 0.3-0.8 mm long; anthers 3.5-5 mm long, connivent, tapering, poricidal at the tips. Ovary sparsely stellate-pubescent in the upper 1/3; style 0.8-1.1 cm long, stout, almost straight or curved at the tip, stellate-pubescent in the lower 2/3-3/4.
Fruits:
Fruit a spherical berry, 2-5 per infructescence, 0.9-1.3 cm in diameter, the pericarp smooth, orange-red at maturity, glabrous; fruiting pedicels 1.2-2 cm long, 1-1.8 mm in diameter at base, woody, pendulous, strongly recurved, with 1-8 prickles; fruiting calyx lobes not elongating, ca. ½ the length of the mature fruit, with 3-20 prickles.
Seeds:
Seeds ca. 15-20 per berry, 2.8-4 mm long, 2.5-3.2 mm wide, flattened-reniform, dull yellow to orange-brown.
Chromosome number:
Not known
Distribution:
Endemic to Ethiopia, primarily in the highlands; growing in montane forest, forest edges, open spaces and steep slopes; 2100-3300 m elevation.
Phenology:
Flowering and fruiting throughout the year.
Phylogeny:
Solanum macracanthum is a member of the Old World Clade of subgenus Leptostemonum (the spiny solanums; Levin et al. 2006) based on morphology and distribution; it has not been included in phylogenetic studies.
References:
Friis, I. 2006a. Solanaceae. In Flora of Ethiopia and Eritrea vol. 5, ed. I. Hedberg et al., 103–160 Addis Addis Ababa: Ababa University; Uppsala: Uppsala University.
Friis, I. 2006b. Solanaceae. In Flora of Somalia vol. 3, ed. M. Thulin, 206-219. Kew: Royal Botanic Gardens, Kew.
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.
Common names and uses:
Local Names. Ethiopia: Umboy (SW Ethiopia Forest Inventory 430).
Taxonomic name:
Solanum macracanthum is a high elevation Ethiopian endemic. Its prominent straight prickles and its fruit over 9 mm in diameter, short petioles, and mostly subentire leaves make it a distinctive member of the Anguivi grade. Long midpoints on the trichomes are usually visible with the naked eye; these are always 0.7-1.5 mm long on the abaxial surface of the leaves but sometimes shorter on the young stem. The epithet “macracanthum” (large prickle) is descriptive of the long straight prickles but can cause confusion as the prickles of the nearly sympatric S. adoense are typically larger and more numerous.
Solanum macracanthum is closely related to the more northern S. adoense and the two species are frequently confused in herbarium collections. They share long, straight and robust yellow prickles on the stem and the calyx. We agree with Friis (2006a, b) but broaden his concept of S. macracanthum to include plants with deeply-lobed leaves, large fruit, and hairs with long midpoints (such as those of the type of S. indicum var. uollense, which was not seen by Friis). Friis (2006a) has overemphasised the spatial separation between S. macracanthum and S. adoense. They are in fact largely sympatric across Gonder region and the central highlands. Solanum macracanthum can be distinguished from S. adoense by its ripe fruit 9-13 mm in diameter (versus 5-8 mm diameter in S. adoense), ellipsoid leaves 2-3.5 times longer than wide (versus ovate to orbicular leaves 1-2 times longer than wide in S. adoense), petiole 1/10-1/5 of the leaf blade length (versus 1/4-1/3 of the leaf blade length in S. adoense), and flowering calyx 7-12 mm long (versus flowering calyx 3-5 mm long in S. adoense).
Solanum macracanthum is also sympatric with S. anguivi across its distribution range, although S. macracanthum tends to grow at higher altitudes. Solanum macracanthum can be distinguished by its ripe fruit that is 9-13 mm in diameter (versus 6-9 mm diameter in S. anguivi), calyx 7-12 mm long (versus calyx 3-5 mm long in S. anguivi), and always undulate or rounded leaf margins (versus leaf margins usually with obtuse or acute lobes in S. anguivi).