Solanum uncinellum
Citation:
Edwards's Bot. Reg. 26: t.15. 1840.
Type:
Cultivated in the “garden of the Horticultural Society” [England, Chiswick], July 1837, Anon. (holotype, CGE).
Written by:
Knapp, S.
Habit:
Large woody vines, climbing to canopy by means of twining petioles. Stems often hollow, minutely puberulent with tiny simple 1-2-celled trichomes to densely pubescent with dendritic trichomes to 1 mm long, the trichomes sometimes enlarged at the base; new growth minutely puberulent to densely pubescent with dendritic trichomes. Bark of older stems dark reddish brown, glabrescent.
Sympodial structure:
Sympodial units plurifoliate, not geminate.
Leaves:
Leaves simple or occasionally pinnately 2-3-lobed, (2.5-)6-15(-20) x (1.5-)3-9(-11) cm, elliptic to narrowly ovate, widest near the middle or in the basal third, coriaceous to chartaceous, the upper surfaces glabrous and somewhat shiny to pubescent with simple uniseriate trichomes along the veins to evenly pubescent on the veins and lamina with dendritic trichomes to 1 mm long, the lower surfaces glabrous (W Ecuador) to minutely simple puberulent to densely dendritic pubescent, the pubescence denser than that of the upper surfaces; primary veins 6-8 pairs, arching conspicuously to the petiole; base acute to truncate or cordate; margins entire or pinnatifid, the lobes to within 0.5 cm of the midrib; apex acute; petiole 1-6 cm, very variable in length along the stem, minutely puberulent to densely pubescent with dendritic trichomes like those of the stems and leaves, especially in the adaxial groove, twining.
Inflorescences:
Inflorescence terminal or sometimes lateral, 4-20(-30+) cm, several times branched, the branches very variable in length, with up to 100 flowers, finely and densely puberulent with tiny simple trichomes to densely pubescent with dendritic trichomes; peduncle 1.5-6 cm, not particularly distinct; pedicels 0.5-1 cm, 0.5-1 mm in diameter at the base, 1.5-2 mm in diameter at the apex, stout, spreading at anthesis, minutely puberulent to densely pubescent like the rest of the inflorescence, the pubescence sparser distally, articulated at the base from a small sleeve leaving a tiny peg on the inflorescence axis; pedicel scars more or less evenly spaced 2-5 mm apart on the flowering parts of the inflorescence rhachis.
Flowers:
Flowers all perfect, 5-merous. Buds narrowly ellipsoid and tapering, with a terminal pointed nipple, the corolla very exerted from the calyx tube early in bud. Calyx tube 1-1.5 mm, conical or broadly conical, the lobes apparently absent or mere apiculae from the rim to broadly deltate, glabrous to very minutely puberulent, the tips with a few uniseriate simple trichomes. Corolla 2-3 m in diameter, purple, violet or white, often with a mixture of colours, fleshy, deeply stellate, lobed nearly to the base, the lobes 12-16 x 1.5-2.5 mm, planar at anthesis, densely papillate on both surfaces with simple trichomes (papillae) to 0.3 mm, or the adaxial surface glabrous with only a few trichomes along the keeled lobe midvein, these giving the flowers a white cast in dried material, the tips cucullate. Filament tube minute, the free portion of the filaments markedly unequal, one anther with a longer filament 2-5 mm, the other 4 anthers with filaments 1-2 mm, glabrous or occasionally minutely puberulent with simple papillae within; anthers 5-8 x 1.5-2 mm, tapering, the base markedly sagittate to hastate, the lobes 0.5-1 mm, tightly connivent, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary glabrous; style 10-13 mm, usually equal in length to the longest anther, densely pubescent in the basal 2/3 (within the anther tube) with tiny dendritic trichomes to 0.5 mm long or very occasionally (W Ecuador) glabrous or only minutely puberulent, held tightly against the anther with the long filament; stigma capitate, occasionally somewhat bilobed, the surface minutely papillate.
Fruits:
Fruit a globose berry, to 2 cm in diameter, red, violet or metallic blue when ripe, not shiny, glabrous, the pericarp thin and leathery; fruiting pedicels to 1.5 cm, ca. 2.5 mm in diameter, apparently erect, but probably hanging from the weight of the berry.
Seeds:
Seeds 20-30 per berry, 3-7 x 2-5 mm, flattened-reniform, the surfaces appearing hairy from the lateral testa cell walls, these to 1 mm long, the testal cells pentagonal.
Chromosome number:
Not known
Distribution:
Widely distributed throughout tropical America from Costa Rica to Argentina, in a wide variety of habitats from lowland rainforest to dry chaco vegetation, from 0-2000 m elevation.
Phylogeny:
Solanum uncinellum (as S. ipomoea) was shown to be a member of the Dulcamaroid clade (Weese & Bohs, 2007). It shares with other members of that clade the vining habit, twining petioles, pedicels in sleeves or platforms, and brightly colored berries.
References:
Linnaeus, C. 1781. Supplementum.
Macbride, J.F. 1962. Solanaceae.
Flora of Peru. Field Mus. Nat. Hist., Bot. Ser. 13(5B): 1-267.
Weese, T.L. & L. Bohs 2007. A Three-Gene Phylogeny of the Genus Solanum (Solanaceae)
Syst. Bot. 32(2): 445-463.
Solanum uncinellum is the oldest name for the species that has variably been called either S. pensile or S. ipomoea, depending upon the type of pubescence (see below). The provenance of the plant grown in the Horticultural Society’s garden in Chiswick (London, England) was not known to Lindley, but from the fact that it was grown outdoors in England it is likely to have been from the southern part of the species range. The lack of branched pubescence may be due to the wet conditions under which it would have been grown in England. The holotype in the Lindley herbarium at CGE is labelled “HHS July 1837” and “S. uncinellum, Bot. Reg. 1840 t. 15” in Lindley’s hand.
Solanum uncinellum is a very widespread and variable species, occurring in a huge range of habitats throughout the American tropics. The extremes of pubescence variation in S. uncinellum look very different, but an entire range of intermediates occur scattered throughout the region; no consistent geographic patterns can be discerned. Even within a single collection (e.g., duplicates of Schomburgk 594), almost glabrous and densely pubescent sheets can be seen. Plants from the southern part of the range (the Chaco of Bolivia, Paraguay and Argentina) are more consistently pubescent with dendritic trichomes and often have cordate leaf bases, and those from western Ecuador have almost completely glabrous leaves. Specimens from the Amazon and Guianas, however, are mostly dendritic pubescent with elliptic leaves or have a mixture of dendritic and simple trichomes of varying densities. Pubescence density and type may depend upon the microclimate or exposure status of the plant or part of plant, as has been observed in other species (e.g., S. confertiseriatum, see Knapp, 2002). Flower morphology is remarkably consistent throughout the range of the species, although flower size varies from plant to plant.
Juvenile leaves of S. uncinellum are not known, but are likely to be pinnate or deeply pinnatifid. A series of sterile specimens from tropical America variously identified as “Solanum dulcamara” (MacBride, 1962) are probably juvenile specimens of S. uncinellum. Some specimens (Rimachi 8110) from the Iquitos area of Peru are densely pubescent like those from the southern portion of the species range, and have pinnate leaves on reproductive stems. Associating juvenile foliage with adult plants of S. uncinellum will be difficult, but would be useful in determining if, like many other members of the clade (e.g., see S. dulcmaroides), this species has pinnate pre-reproductive leaf morphology.
Solanum uncinellum is not easily confused with any other Neotropical Solanum species; the elongate flower buds with an apical nipple, narrowly stellate corollas and large complex inflorescences are all distinctive. In fruit it could be confused with other members of the Dulcamaroid clade, but short petioles and “hairy” seeds distinguish it from any other South American species. “Hairy” seeds also occur in S. dulcamaroides and S. seaforthianum, but those taxa differ from S. uncinellum in flower shape (neither of them are deeply stellate with narrow corolla lobes) and morphology (only S. seaforthianum has unequal filaments, but not as pronounced as in S. uncinellum) and in leaf characters. The leaves of S. seaforthianum are glabrous and pinnate, while those of S. uncinellum are usually variously pubescent; the leaves of S. dulcamaroides have a promounced submarginal vein.
Solanum flaccidum, with which S. uncinellum is sympatric in the southeastern part of its range, also has anthers borne on unequal filaments, but in that species the anthers are ellipsoid, not tapering, and the long filament is less than twice the length of the rest of the filaments, whereas in S. uncinellum the long filament is approximately two times the length of the rest. The corollas of S. flaccidum are also more rotate than those of S. uncinellum, with broader lobes.
From specimen labels it appears that S. uncinellum has red, purple or metallic blue berries when ripe. Fruiting collections with ripe berries are not especially common, and these color differences do not appear to have a geographic component. It may be that berry color changes through development, as has been observed in other species such as S. nitidum (also of the Dulcamaroid clade; see Knapp, 1989).
Linnaeus described S. scandens using collections of C.G. Dalberg from Surinam, and the lectotype specimen is likely to be a Dalberg collection, although there is no direct evidence on the sheet that Dalberg actually collected it. In 1781, Linnaeus filius included a S. scandens in his Supplementum (Linnaeus, 1781), which has often been taken as the coining of a new name. Bearing in mind the materials available to Linnaeus filius, his direct citation of a Dalberg specimen and the fact that LINN 248.24 is the only sheet of S. uncinellum in the Linnaean herbarium, it is clear that rather than coining a new name, Linnaeus filius was including his father’s S. scandens in his treatment.
Many of the synonyms of Solanum uncinellum are described from large numbers of syntype specimens and will need to be carefully lectotypified.
The holotype of Solanum palenquense at MO and an isotype at US both have stems with markedly bicolorous leaves attached mounted on the sheet and loose flowers (and fruit) in a packet. Michael Nee (pers. comm.) has suggested that the finely ridged stems and petioles plus the sharp tooth-like tips of the nearly entire margin show the leafy stems are from a plant of Piptocarpha poeppigiana (DC.) Baker (Asteraceae). The flowers in the packets on both sheets are definitely those of S. uncinellum and the logical lectotype would be the contents of the packet of the MO sheet. The mixed collection is certainly due to the canopy vine status of both taxa.