Solanum triquetrum (Knapp, Sandra 2013)
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Ordo: Solanales
Familia: Solanaceae
Genus: Solanum
Name
Solanum triquetrum Cav., Icon. Pl. 3: 30, tab. 259. 1795 – Wikispecies link – Pensoft Profile
- Solanum triquetrum Knapp, Sandra, 2013, PhytoKeys 22: 1-1.
Description
Description. Semi-woody vine or scrambler with an enlarged woody base, to 2 m long, occasionally an erect subshrub to 0.5 m tall. Stems somewhat angled, glabrous to pubescent with weak simple uniseriate trichomes to 0.5 mm long, these usually ascending and pointing to the distal part of the stems; new growth sparsely to densely pubescent with simple uniseriate trichomes to 0.5 mm long, but usually shorter. Bark of older stems pale greenish yellow. Sympodial units plurifoliate. Leaves simple to basally lobed and hastate, (1.1-)1.8-5(+) cm long, (0.3-)1-3.5 cm wide, deltate to hastate, triangular in outline, sometimes linear, slightly fleshy, the upper and lower surfaces pubescent with simple uniseriate trichomes along the margins and on the veins to uniformly pubescent on the veins and lamina, the trichomes to 0.5 mm long, white; primary veins 3-5 pairs, only just visible in dried material, sometimes slightly impressed above; base abruptly truncate to hastate with 2 basal lobes to 1 cm long, these rounded at the tip; margins entire to basally lobed; apex acute to acuminate, the tip sometimes rounded; petioles 0.3-1.2 cm long, glabrous but with a line of simple trichomes adaxially, apparently only sometimes twining. Inflorescences terminal or lateral, 1-3 cm long, usually simple, very occasionally furcate, with 3-6 flowers, glabrous to pubescent like the stems, the pubescence like that of the rest of the plant; peduncle 0.3-1 cm long; pedicels 0.6-1.2 cm long, ca. 0.5 mm in diameter at the base, ca. 1 mm in diameter at the apex, slender, sometimes tinged purple, glabrous to sparsely pubescent with simple uniseriate white trichomes, articulated at the base from a short sleeve 0.5-1 mm deep; pedicel scars irregularly spaced 1-4 mm apart. Buds when young globose, later ellipsoid, the corolla strongly exserted from the calyx tube before anthesis. Flowers all perfect, usually 5-merous. Calyx tube 1-1.5 mm long, conical, the lobes 1.5-2 mm long, triangular with the tips often long-acuminate, often purplish tinged, glabrous to sparsely pubescent abaxially, densely papillate adaxially, pubescent with simple trichomes to 0.2 mm on internal surface of tips. Corolla 1.5-1.9 cm in diameter, white or tinged with purple, often with a shiny green or greenish white eye, stellate, lobed nearly to the base, the lobes 0.8-0.9 mm long, ca. 0.3 cm wide, reflexed at anthesis, the midvein often tinged purple, glabrous to sparsely pubescent abaxially especially along the distal margins and tips, glabrous adaxially. Filament tube minute, the free portion of the filaments ca. 1 mm long, glabrous; anthers 3.5-4 mm long, 1-1.5 mm wide, ellipsoid, loosely connivent, poricidal at the tips the pores lengthening to slits with age. Ovary glabrous; style 6-8 mm long, glabrous; stigma capitate to somewhat clavate, the surface minutely papillose. Fruit a globose to slightly ellipsoid berry, to 1.5 cm in diameter, bright red when ripe, the pericarp thin and shiny, glabrous; fruiting pedicels 1-1.5 cm, ca. 1 mm in diameter at the base, somewhat woody, deflexed or spreading. Seeds (2-)6-10 per berry, ca. 4 mm long, 2.5 mm wide, flattened to thickened reniform, reddish brown, the surfaces minutely pitted, in mature fruits the lateral testal cell walls exposed and the seed prominently silky, the testal cells rectangular to slightly sinuate. Chromosome number: not known.
Distribution
Distribution (Figure 98). In the USA in central, south and west Texas and northern Mexico, south to the state of Coahuila, from sea level to 500 m elevation.
Discussion
Discussion. Solanum triquetrum, like most other members of the Dulcamaroid clade, has incredibly variable leaf morphology. Leaves vary from small, triangular in outline (hence the specific epithet meaning three -angled) and simple to quite deeply lobed at the base to very rarely pinnatifid with two or three pairs of lobes. Leaf size also varies a great deal, perhaps in response to moisture, some specimens with particularly large leaves appear to have been collected in wetter microhabitats. The only species in North America with which Solanum triquetrum could be confused is Solanum dulcamara, an introduced European taxon. Solanum triquetrum differs from Solanum dulcamara in its free anthers, more pointed leaves, strongly angled stems and smaller flowers. Both species have a green "eye", often with shiny white margins, at the center of the corolla at the base of the stamens. Solanum triquetrum usually has white flowers, while Solanum dulcamara has purple flowers, but white-flowered plants of Solanum dulcamara occur throughout its range, both native and introduced. Like Solanum dulcamara, Solanum triquetrum arises from a subterreanean woody rootstock and may die back in winter or in particularly dry seasons. Knapp (2007) lectypified Solanum triquetrum with a sheet cultivated at MA; the fragment at F was taken from the MA sheet and is thus an isolectotype. The location of the type of Solanum lindheimerianum is somewhat problematic. Ferdinand Lindheimer and J. J. Roemer collected together in Texas in 1846, and Roemer gave his collections and many duplicates of Lindheimer's to Scheele, a clergyman from near Hildesheim, Germany. Scheele described many of Lindheimer's plants before Engelmann and Gray had a chance to do so, and duplicates of these collections were only distributed in the early 20th century (Blankinship 1907). The location of Scheele's herbarium and types is not known, but it is likely they were retained by Roemer in Berlin. Fortunately many duplicates of Lindheimer's Texas collections were distributed by Engelmann and Gray. The sheet from the Engelmann herbarium at MO [MO-3938181] has a label in Lindheimer's hand with the date "August 1846" and the locality "New Braunfels" and is the logical choice for a lectotype for Solanum lindheimerianum. A BM sheet dated 1846 is clearly a duplicate of that gathering based on its morphology. The numbering of Lindheimer's collections is of two sorts: 1) Lindheimer's field collection numbers, and 2) the exsiccatae numbers given after the plants were organized into taxonomic sequence and applied to plants of the "same" species collected on several dates (Blankinship 1907). Confusion over duplicates can arise when one or the other number is not cited. For Solanum lindheimerianum the exsiccatae number is 481, while Lindheimer's field collection number is 312. Blankinship (1907: 145) published the combination "S. triquetrum Cav. var. Lindheimerianum Gray", citing Lindheimer 312 (along with other Lindheimer collections) and pointed out that the two taxa were almost certainly synonyms. Asa Gray apparently did not publish this combination formally, but as Blankinship (1907) made explicit reference to Scheele's publication of Solanum lindheimerianum, the correct citation for the variety is Solanum triquetrum var. lindheimerianum (Scheele) A. Gray ex Blankinship.
Taxon Treatment
- Knapp, Sandra; 2013: A revision of the Dulcamaroid Clade of Solanum L. (Solanaceae), PhytoKeys 22: 1-1. doi
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