2. Cosmos parviflorus (Jacq.) Pers.

Pl. 276 g, h; Map 1167

Stems 25–90 cm long, glabrous or sparsely to moderately pubescent with minute, mostly spreading hairs, rarely minutely roughened to the touch. Leaves sessile or with a short petiole to 5 mm long. Leaf blade 1–7 cm long, 1 or 2 times deeply pinnately divided, the ultimate segments narrowly linear, often threadlike, 0.5–1.5 mm wide. Involucre 7–12 mm long, 5–10 mm in diameter, the outer series of bracts 5–9 mm long, spreading to loosely ascending, lanceolate, tapered to a sharply pointed tip, rarely with slender, white margins; the inner series of bracts 6–10 mm long, erect or strongly ascending, oblong to oblong-ovate, rounded or more commonly angled to a bluntly or sharply pointed tip, mostly with relatively broad, white margins. Ray florets with the corolla 0.5–1.5 cm long, most commonly pink, less commonly white or purple. Disc florets with the corolla 4–5 mm long, yellow. Fruits 7–16 mm long (including the beak), the surface glabrous or appearing minutely roughened (with minute, ascending teeth or hairs). 2n=24. July–October.

Introduced, known thus far only from the city of St. Louis (Arizona, New Mexico, Colorado, and Texas; Mexico; introduced sporadically east to Maine). Railroads.

This species was first reported for Missouri by Mühlenbach (1979), based on plants found during his surveys of the St. Louis railyards. It is not widely cultivated.