1. Selenia aurea Nutt. (selenia, golden selenia)

Pl. 326 g, h; Map 1388

Plants annual, terrestrial, glabrous. Stems 5–30(–40) cm long, erect or ascending, sometimes branched from the base. Leaves alternate and basal, 2–6(–9) cm long, the basal leaves short-petiolate, the stem leaves sessile, the bases not clasping the stem, the blades oblanceolate to broadly elliptic in outline, pinnately divided into 5–29 narrow, entire or toothed lobes. Inflorescences racemes, the flowers subtended by reduced, leaflike bracts. Sepals 4–6 mm long, narrowly oblong to ovate, erect. Petals 8–11 mm long, not lobed, yellow. Styles 5–10 mm long. Fruits erect or ascending, 10–25 mm long, oblong or elliptic, less than 2 times as long as wide, flattened parallel to the septum, the margins entire to slightly wavy, dehiscing longitudinally, the valves lacking midnerves, the stalk 1.0–2.5 cm long. Seeds 6–12 per fruit, in 2 rows in each locule, 2.7–3.1 mm long, circular in outline or nearly so, flattened, the margins broadly winged, the surface with a netlike or honeycomb-like pattern of ridges and pits, orange. 2n=46, 138. April–May.

Scattered in the Ozark and Unglaciated Plains Divisions (Missouri, Kansas, Oklahoma). Glades, rocky prairies, thin-soiled areas of pastures, and open, disturbed areas, on sandstone and chert.

This showy species has a relatively restricted range and is the only polyploid taxon thus far documented in a genus whose base numbers appear to include both and (Al-Shehbaz, 1988). Its origin and relationships to the other members of this small genus are poorly understood.