Citation:
in Mart., Fl. Bras. 10: 85. 1846.
Type:
Bolivia. Santa Cruz: Chiquitos, Oct 1850, A. d’Orbigny 1068 (holotype BR; isotypes, G-DC, P, W).
Habit:
Shrubs 1-3 m, erect, much-branched, armed; stems terete, sparsely prickly, the prickles 0.2-0.5 cm, reddish, flattened at the base, curved at the tip, the scar oval, pubescence scabrous to tomentose in young plants, the trichomes porrect stellate, sessile or stipitate, rotate to multiangulate, the rays glandular or not, ochraceous to rusty, older plants glabrescent; new growth densely ferruginous pubescent with sessile stellate trichomes, the midpoints multicellular; bark of older stems brownish red, sparsely pubescent, the stellate trichomes with a 1-2-celled midpoint longer than the lateral rays.
Sympodial structure:
Sympodial units plurifoliate.
Leaves:
Leaves simple, 6-18 x (3-)5-8(-11) cm, oblanceolate, obovate, rhombic, elliptic or ovate-elliptic, chartaceous, discolorous, sometimes the young leaves prickly, the upper surfaces rugose, scabrous or tomentose, the trichomes porrect stellate, rotate, sessile or stalked, with 6-8 lateral rays, the midpoint 1-multicellular, persistent or deciduous, the lower surfaces tomentose-velutinous, grey or yellowish cream, with the midrib prominent; base cuneate, assymetric, slightly decurrent on the petiole; margins entire in adult plants, lobed or angulate in juvenile plants; apex acute; petiole 1-2 x 0.2-0.4 cm, with rusty trichomes like those of the stems.
Inflorescences:
Inflorescences opposite the leaves, 5-15 cm long, branching 2-3 times, with many flowers, golden or rusty tomentose, the trichomes porrect stellate like those of the stems but larger; peduncle 1-4 cm, unarmed; pedicels 0.5-0.7(-0.8) x 0.1 cm, pubescent like the stems and inflorescence, lengthening in fruit, ca. 0.3 mm in diameter, articulating at the base; pedicel scars 2-10 mm apart, slightly raised and oblique. Buds oval, the corolla exserted from the calyx tube at anthesis
Flowers:
Flowers heterostylous, the basal flowers long-styled and perfect, the distal flowers short-styled and staminate; calyx tube 1.5-2(-4) mm, the lobes 4-6 x 1-2.5 mm, oblong to linear-lanceolate, acute to acuminate, both tube and lobes pubescent abaxially with porrect stellate trichomes like those of the rest of the inflorescence with relatively short rays, adaxially glabrescent with a few stellate trichomes in the distal ¼ of the lobes; corolla 2.5-3 cm in diameter, white, stellate, lobed nearly to the base, the lobes 1-1.2 x 0.1-0.3 cm, linear lanceolate, reflexed at anthesis, tomentose abaxially, the trichomes porrect stellate, sessile or stipitate, with or without an apical gland, similar to those of the abaxial leaf surfaces but with larger rays; filament tube 0.8-1 mm, the free portion of the filaments 1-1.5 mm; anthers 8-10 mm, poridical at the tips, the pores obverse, not lengthening to slits; ovary 1.5-2 mm in diameter, hirsute with a mixture of porrect stellate trichomes with an antrorse multicellular glandular midpoint and glandular simple trichomes; style 10-15 mm in perfect flowers, white, straight or curved, 4-5 mm in staminate flowers, glandular puberulent in the basal ¼ to 3/4; stigma clavate, dark-green, papillate.
Fruits:
Fruit a subglobose berry, 1.5-2 cm in diameter, the pericarp glandular-viscous, the trichomes simple, glandular; fruiting pedicels 0.8-1 cm, pendant on the rachis.
Seeds:
Seeds 4-4.5 x 3-3.5 mm, ca. 2 mm wide near the apex, ca. 1 mm thick, flattened reniform, beige to brown, the testa undulate-reticulate.
Phenology:
Flowering and fruiting specimens have been collected throughout the year.
As delimited here, Solanum rhytidoandrum can be recognised by its shrubby habit, heavily armed stems, corymbose inflorescences with more than 10 flowers, white corolla 2.5-3 cm in diameter and hirsute ovary. Solanum rhytidoandrum shares the overall aspect of the plant and leaves with S. decorum, at least in some specimens. They can be differentiated by the redder pubescence of S. decorum that is composed of porrect stellate trichomes with reduced midpoints, as opposed to the rusty pubescence of S. rhytidoandrum composed of stellate trichomes with multicellular midpoints.
Leaf shape and pubescence vary considerably in Solanum rhytidoandrum. Material from Bolivia is quite homogenous in being tomentose with persistent or deciduous (Steinbach 783) trichomes, reduced midpoints that are rarely multicellular (Daly et al. 2259). The leaves are larger, ovate, ovate-elliptic or even rhomboid (Nee 33898), with lobed-angulate (Nee 38582, 35898), sinuate (Hassler 8363) or entire (d’Orbigny 1068) margins. Leaf shape and margin can vary within an individual plant (Nee 35898, 37680). The flowers and calyx lobes are larger in Bolivian collections than in the rest of the range. The fruit has a leathery pericarp, with sparse sessile or stalked trichomes (Nee 38582, Daly et al. 2259). Material from northeastern Brazil generally has elliptic to ovate-elliptic leaves and smaller flowers (ca. 2.5 cm in diameter). The pubescence is tomentose, with porrect stellate trichomes with a midpoint that is unicellular or multicellular. In some specimens from the brejos of Pernambuco (ABC 665, 970) porrect stellate trichomes with a glandular midpoint occur on the pedicel. Some collections from Ceará (Drouet 2643, 2276) have more elliptic leaves and the fruit pubescence consists of sparse stellate and glandular trichomes; specimens intermediate with these types have been collected in Goiás. Looking at the two extremes of character combination might lead one to consider these forms distinct, but the continuous variation between these extremes is evidence that they should be treated as one, highly variable, taxon.
Solanum baturitense was described by Huber in 1901, but without an illustration or indication of which herbarium the specimens he examined were held. The name was missed from Index Kewensis, and after an exhaustive search in Brazilian and international herbaria, a specimen that can be considered the holotype was found in the general collections of the Museu Goeldi, in Belém. Although the name has been widely used, the type specimens fall within the variation here defined for S. rhytidoandrum, and it is here synonymised. Solanum apaense also falls within the wide variation of S. rhytidoandrum, despite its apparently more open and larger inflorescences with larger flowers. Variation like that observed in these synonyms has also been observed in the field, especially in individuals growing in wetter microhabitats.