United States of America. Nebraska: Hooker County, on Middle Loup River, near Mullen, 20 Jul 1893, P.A. Rydberg 1385 (lectotype, designated here: NY [NY00138953] isotypes: GH [GH00077424], H [acc. # 1087075], NDG [NDG45091], NEB [NEB-V-0000607], NY [NY00138952], US [US00027625, acc. # 210385; US02828882, acc. # 210353]).

Annual herbs to subwoody perennial shrubs up to 1.0 m tall, branching at base. Stems terete to ridged, pale straw colour, sparsely pubescent with simple, appressed, uniseriate (2)4–8-celled trichomes, these ca. 0.6 mm long, the new growth more densely pubescent. Sympodial units difoliate, the leaves not geminate. Leaves simple, 4.5–11.2 cm long, 2.3–6.8 cm wide, ovate to broadly ovate, membranous, green on both sides; adaxial surface sparsely pubescent with appressed translucent, simple, uniseriate trichomes like those on stem scattered along veins and lamina; abaxial surface more densely pubescent with trichomes like those of the upper surface across both lamina and veins; primary veins 4–6 pairs; base attenuate; margins sinuate dentate, especially so up to 2/3 from the base, to occasionally entire; apex acute to acuminate; petiole 0.5–3.5 cm long, pubescent with simple uniseriate trichomes like those of the stems. Inflorescences 2.4–3.5 cm long, lateral, internodal, unbranched or rarely forked, with (2)3–8 flowers clustered near the tips (sub-umbelliform) or less commonly the distal flowers spaced along the rhachis, the lowermost flower distant from the rest, sparsely pubescent with appressed simple uniseriate trichomes like those on stem, rhachis 2–10 mm long when present; peduncle 1.0–2.0 cm long, straight; pedicels 5–8 mm long, 0.3–0.4 mm in diameter at the base and 0.4–0.5 mm in diameter at the apex, spreading, the terminal pedicels articulated at the base, but the lowermost flower with the pedicel articulated in the basal 1/4 to 1/3; pedicels spaced 0–1.0 mm apart. Buds globose, corolla exserted from the calyx 1/5 to 1/3. Flowers 5-merous, all perfect. Calyx tube 1.0–1.5 mm long, lobes irregularly unequal, the longest 1.7–4.5 mm long, 0.6–0.7 mm wide, lanceolate with acute to acuminate apices, sparsely pubescent with appressed hairs like those on stem but shorter. Corolla 6–12 mm in diameter, stellate, white with a yellow-green central portion near the base, lobed 1/2 to 2/3 to the base, the lobes 4.0–5.0 mm long, 2.0–3.0 mm wide, strongly reflexed at anthesis, later spreading, densely pubescent abaxially with simple uniseriate trichomes like those on stem and leaves but shorter. Stamens equal; filament tube minute; free portion of the filaments 0.7–1.0 mm long, pubescent with tangled uniseriate simple trichomes; anthers 1.8–2.5 mm long, 0.6–0.9 mm wide, ellipsoid, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary globose, glabrous; style 3.5–4.5 mm long, exserted 0–1 mm beyond anther cone, densely pubescent with 2–3-celled simple uniseriate trichomes along 2/3 from the base; stigma capitate, minutely papillate, green in live plants. Fruit a globose berry, 10–14 mm in diameter, purple-black at maturity, opaque, the surface of the pericarp shiny; fruiting pedicels 6–10 mm long, 0.4–0.6 mm in diameter at the base, 0.6–1.0 mm in diameter at the apex, recurved to reflexed, pedicels spaced 0.5–2.5 mm apart, dropping with mature fruits, occasionally not dropping; fruiting calyx not accrescent, the tube 1.5–2.0 mm long, the lobes (2.0–)3.0–4.0 mm long with the apices spreading to strongly reflexed in fruit. Seeds 20–40 per berry, 1.8–2.0 mm long, 1.5–1.6 mm wide, flattened and tear-drop shaped with a subapical hilum, yellow, the surfaces minutely pitted, the testal cells pentagonal in outline. Stone cells 2–4, 0.8–1.0 mm in diameter, white or cream coloured. Chromosome number: 2n=2×=24 (Heiser et al. 1965).

(Figure 23) Solanuminterius is endemic to North America, and the most common species of morelloid in the Great Plains. It is less common west of the Rocky Mountains, and although it does extend to Arizona and western New Mexico, S.interius does not occur on the Gulf Coast where it is replaced by S.nigrescens. Records of S.interius for Canada (Saskatchewan, Harms 2006) have not been verified with voucher specimens, although it is to be expected there. Specimens annotated by Harms as S.interius in SASK are of S.emulans (e.g., Child s.n., collected 29 July 1941)

Solanuminterius is found in open habitats in sand hills and low forest, often in shade under trees between (100-)500 to 2,500 m elevation.

United States of America. Deadly nightshade (USDA Plants 2017), Inland nightshade, Plains black nightshade, morelle de l’interieur (NatureServe 2017), Yerba mora negra (New Mexico, Hill 14851).

None recorded on herbarium labels; Heiser (1969; quoting Charles Bessey) quotes “a young man from Fort Dodge, Iowa spoke up and said that the people in his neighbourhood made them [berries of “S.nigrum”] into pies, preserves, etc. and ate freely of them.” Bessey (quoted in Heiser 1969) went on to say that later he found that in central and western Iowa nightshades were indeed eaten; it is possible these were the berries of S.interius.

Least Concern (LC). Solanuminterius is widespread through the Great Plains region in the United States of America. For EOO see Table 6.

Solanuminterius can be distinguished from other North American morelloids by its inflorescence with apparently uneven branches, one with several flowers and the other apparently with a single flower that is actually the basal flower with the articulation ca. 1/4 to 1/3 of the way up the pedicel, very like the pedicel articulation in wild potatoes. Other distinguishing features to be used in combination with this are the medium-sized anthers 1.8–2.5 mm long and relatively long rectangular calyx lobes with rounded apices. Solanumnigrescens has more regularly spaced flowers, occasionally branched inflorescences with more than one flower per branch and is more common along the Gulf Coast but distinguishing the two species without locality information can be difficult. The seeds of S.interius are much larger than those of S.nigrescens (1.8–2 mm versus 1.2–1.5 mm long) or any other of the diploid morelloids occurring in the area. Stone cell number can also be used as a distinguishing character; S.interius has 2–4 stone cells in each berry while S.nigrescens has more than 6 and often as many as 12.

Solanuminterius is sympatric with S.emulans and can be distinguished from that species in its longer anthers (1.8–2.5 mm long versus 1.5–1.8 mm long), its rounded calyx lobe apices, and its larger berries (10–14 mm in diameter versus 6–8 mm in diameter) with larger seeds (1.8–2.0 mm long versus 1.6–1.8 mm long). The flowers of S.emulans are usually smaller than those of S.interius. Nee (on label of Nee 61337) says that living plants of the two species are quite distinct, and that S.interius is a perennial growing in the shade of single trees.

In describing S.interiusRydberg (1905) cited a collection but no herbarium. We have selected the sheet in the herbarium (NY) where he worked (NY00138953) that is annotated “Type” as the lectotype of this species following best practice as described in McNeill (2014).

See Suppl. materials 1 and 3.