Novon 2: 344. 1992.
Perú. Amazonas: Bagua, Quebrada Chinganza, 8 km N of Muyo, km 472 of Oleoducto Norperuano, 350-400 m, 5 25'S, 78 28'W, 5 Jul 1984, Knapp & Mallet 6564 (holotype, USM; isotypes, BH, F, K, US).
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Slender shrubs to small trees, 1-7 m tall; young stems and leaves densely pubescent with dendritic trichomes, these 0.5-1 mm long, pale golden when dry, beige when fresh; bark of older stems reddish-brown, sparsely pubescent with dendritic trichomes.
Sympodial units difoliate, geminate, anisophyllous.
Leaves glabrous and shining adaxially, with a few dendritic trichomes along the main veins, pubescent with dendritic trichomes abaxially, the pubescence denser along the veins; major leaves elliptic-obovate to obovate, 17-26 cm long, 8-15 cm wide, with 9-13 pairs of main lateral veins, the apex acute to acuminate, the base sessile and truncate, occasionally somewhat auriculate; petiole if present ca. 2 mm long; minor leaves differing from the majors in both size and shape, orbicular, 3-7.5 cm long, 3-7 cm wide, the apex rounded, the base rounded; petioles 1-2 mm long.
Inflorescences opposite the leaves, simple, 1-15 cm long, 10-15-flowered at a time, but with up to 100 scars, densely pubescent with dendritic trichomes; pedicel scars densely spaced, not overlapping. Buds globose, the corolla strongly exserted from the calyx tube, densely pubescent with dendritic trichomes. Pedicels at anthesis somewhat deflexed, strongly contracted beneath the calyx tube, ca. 1 mm in diam. at the apex, 0.5 mm in diam. at the base, 0.7-1 cm long, densely pubescent with dendritic trichomes like those of the rest of the inflorescence.
Flowers with the calyx tube broadly conical, 1.5-3 mm long, the lobes triangular, 1.5-3 mm long, densely pubescent with dendritic trichomes; corolla pale green, 1-1.2 cm in diam., lobed ca. 3/4 of the way to the base, the lobes planar at anthesis, the abaxial surface of the lobes densely dendritic-pubescent; anthers 2-2.5 mm long, 1.5-2 mm wide, in the type with a few dendritic trichomes on the abaxial surface, poricidal at the tips, the pores tear-drop shaped; free portion of the filaments ca. 0.25 mm long, the filament tube ca. 0.5 mm long; ovary densely pubescent with dendritic trichomes ca. 0.5 mm long; styles heteromorphic, in short-styled flowers 1-1.5 mm long, in long-styled flowers 5-6 mm long; stigma clavate, the surface minutely papillose.
Fruit a globose, green berry, 1-1.2 cm in diam.; fruiting pedicels woody, erect or deflexed, 0.7-1 cm long, ca. 1.5 mm in diam. at the base.
Seeds reddish-brown, flattened-reniform with the margins incrassate and paler, 1-3 mm long, 1.5-2.5 mm wide, the surfaces minutely pitted.
On the W margin of the Amazon basin in Colombia, Ecuador and Perú, in tropical wet forest, from 200-1300 m.
Solanum malletii is a member of the Solanum nutans species group (Knapp, 2002) of the Geminata clade (Bohs, 2005).
Knapp, S. 2002. Solanum section Geminata (G. Don) Walpers (Solanaceae).
Flora Neotropica 84: 1-405.
Bohs, L. 2005. Major clades in Solanum based on ndhF sequences.
Pp. 27-49 in R. C. Keating, V. C. Hollowell, & T. B. Croat (eds.), A festschrift for William G. D’Arcy: the legacy of a taxonomist. Monographs in Systematic Botany from the Missouri Botanical Garden, Vol. 104. Missouri Botanical Garden Press, St. Louis.
Solanum malletii can easily be distinguished from other members of the S. nutans species group by its orbicular minor leaves and auriculate major leaf bases. The elongate, densely pubescent inflorescences of this species are like those of S. youngii, but S. malletii is easily distinguished from that species by its non-bullate leaves, orbicular minor leaves, and low elevation habitat.
The prescence of short-styled flowers in S. malletii (see Fig. 74B in Knapp, 2002) indicates that it is probably andromonoecious, but this has yet to be tested in the field.