1. Melochia corchorifolia L. (chocolate weed)

Pl. 455 d, e; Map 2063

Plants annual (perennial herbs and subshrubs elsewhere). Stems 10–60(–120) cm long, loosely ascending to more commonly erect, often branched from the base, sparsely pubescent with minute stellate hairs and sometimes also scattered simple or fasciculate hairs, especially near the nodes. Leaves short- to long-petiolate (those of axillary fascicles often very short-petiolate), the blades 0.8–6.0 cm long, 0.5–2.5 cm wide, oblong-lanceolate to ovate, rounded to shallowly cordate at the base, rounded to more commonly bluntly or sharply pointed at the tip, unlobed or rarely very slightly 3-lobed, the margins toothed. Stipules mostly persistent at maturity, 2–6 mm long, linear. Flowers small, dense clusters, these axillary and/or terminal (then sometimes forming an irregular raceme, the bractlets subtending the calyx 4–6, 4–7 mm long, linear, bristly-hairy along the margins. Calyces 2.0–2.8 mm long at flowering, not becoming enlarged or inflated at fruiting, the sepals fused to above the midpoint, the lobes more or less ascending, broadly triangular with broad, U-shaped sinuses and sharply pointed tips, not overlapping, the calyx not appearing angled or winged. Petals relatively small but conspicuous, 4.0–6.5 mm long, the tips shallowly notched to truncate or broadly and very bluntly pointed, often slightly irregular, the margin otherwise entire or nearly so, light pink to nearly white (sometimes turning reddish as the flowers fade). Stamens 5, the staminal column circular in cross-section, without a low crown of teeth at the tip, the anthers yellow, positioned opposite the petals. Pistils with 5 locules. Styles 5, separate, each with a linear to slightly club-shaped stigmatic area toward the tip. Fruits bluntly 5-lobed capsules, these 3.5–5.0 mm long, depressed-globose, beakless, dehiscing longitudinally between the valves and usually shattering completely at maturity, each locule 1- or 2-seeded, the valves variously green to reddish brown or dark brown at maturity, smooth-walled, but hairy. Seeds 2–3 mm long, asymmetrically ovate-elliptic in profile, wedge-shaped in cross-section, dark brown, glabrous, but usually with a thin, papery, lighter brown covering, this eroding irregularly to expose the underlying seed coat. 2n=36, 46. August–October.

Introduced, known thus far only from St. Louis City (native of Africa and Asia south to Australia, introduced sporadically in the eastern [mostly southeastern] U.S. and also tropical America). Railroads.

This species was reported by Mühlenbach (1979) from his botanical inventory of the St. Louis railyards. It has not been seen as an escape in Missouri since the original documentation.