1. Tidestromia lanuginosa (Nutt.) Standl. ssp. lanuginosa

Pl. 199 c, d; Map 829

Plants annual (perennial herbs elsewhere). Stems 10–60 cm long, spreading to very loosely ascending, usually reddish purple, without longitudinal lines or ridges, densely pubescent with stellate hairs, sometimes the lower portion becoming nearly glabrous with age, the nodes somewhat swollen. Leaves opposite (rarely whorled toward the stem tip, rarely alternate toward the base), short- to long-petiolate, those of a pair usually joined by an inconspicuous ridge around the node. Leaf blades 0.5–3.0 cm long, somewhat thickened and leathery, obovate to spatulate or nearly circular, narrowed or tapered at the base, rounded or bluntly pointed at the tip, the margins entire, the surfaces densely pubescent with stellate hairs, appearing grayish green, sometimes becoming nearly glabrous with age. Inflorescences in small, sessile, axillary clusters of 2–5 flowers. Bracts similar in texture but about 1/3 as long as the sepals, papery or scalelike, hairy. Flowers perfect. Sepals 5, free, 1–3 mm long, the outer 3 larger than the inner 2, lanceolate to narrowly ovate, tapered to a sharply pointed but unawned tip, papery or scalelike, translucent, straw-colored to yellow to yellowish brown, hairy, sometimes becoming glabrous and shiny at maturity. Stamens 5, the filaments fused toward the base, usually alternating with 5 minute, triangular teeth. Ovary more or less globose. Ovule 1. Style short, persistent, the stigma 1, capitate, sometimes somewhat 2-lobed. Fruits with rigid walls, 1.5–2.0 mm long, more or less globose, tapered abruptly to the minute beak, glabrous, indehiscent, 1-seeded. Seeds 1.2–1.6 mm long, more or less globose, the surface yellowish brown, shiny. July–October.

Introduced, known only from historical collections from Jackson County (southwestern U.S. east to South Dakota and Louisiana; Mexico, Caribbean Islands; introduced in Illinois, Missouri, and Pennsylvania). Railroads and open, disturbed areas.

The recently segregated ssp. eliassoniana Sánchez-del Pino & Flores Olvera includes plants of the southwestern United States and adjacent Mexico that differ from ssp. lanuginosa in having microscopically spiny (vs. smooth) pollen grains and in subtle details of trichome morphology.