8. Solanum citrullifolium A. Braun, Index Seminum (Friburg). 1849: [3]. 1849.
[W]
Watermelon or melon-leaf nightshade
Herbs, annual, spreading, sparsely to moderately armed, 0.3–0.8 m, prickles yellowish, straight, needlelike, 3–7 mm, sparsely to densely pubescent, hairs short, unbranched, glandular, occasionally with a few longer, unbranched, eglandular hairs, abaxial leaf surfaces usually also with sessile to short-stalked, few-rayed, stellate hairs, central ray equal to or longer than lateral rays. Leaves petiolate; petiole 2–7 cm; blade simple to compound, broadly ovate, 4–10(–15) × 3–8 cm, margins bipinnately lobed or divided with 3–4 main leaflets per side, these with obtuse or rounded lobes, base truncate. Inflorescences extra-axillary, unbranched, 4–10-flowered, 3–11 cm. Pedicels 1–2 cm in flower, 1–2 cm and erect in fruit. Flowers bilaterally symmetric; calyx accrescent and tightly covering fruit, densely prickly, 2.5–3.8 mm, densely glandular-pubescent, lobes linear-lanceolate; corolla violet or blue, pentagonal-stellate, 2.5–3.5 cm diam., with interpetalar tissue at margins and bases of lobes; stamens unequal, lowermost much longer and curved; anthers narrow and tapered, dehiscent by terminal pores, short anthers yellow, 6–10 mm, longer anther purplish, 11–16 mm; ovary glabrous. Berries brown, globose, 0.8–1.2 cm diam., glabrous, dry, without sclerotic granules. Seeds dark brown, flattened, 2.3–3 × 2–2.5 mm, reticulately wrinkled, ridged, or undulate. 2n = 24.
North American plants identified as Solanum heterodoxum Dunal are largely misidentifications of S. citrullifolium. Solanum heterodoxum in the current sense is now restricted to Mexico.
Varieties 2 (2 in the flora): sc, se United States, Mexico.
