Herbs or subshrubs, perennial, usually monoecious, rarely dioecious, to 6 dm. Stems erect, hairy, hairs malpighiaceous. Leaves: stipules deciduous, elliptic, 0.3–0.4 mm, margins not glandular; petiole absent; blade ovate, elliptic, or obovate, 1.6–7.5 × 0.4–3.8 cm, margins entire or undulate, without glands, surfaces hairy, hairs malpighiaceous. Inflorescences bisexual, 3.5–12 cm; bracts elliptic, 1–1.5 mm, margins without glands. Flowers without pink dye when wetted. Staminate flowers: sepals narrowly elliptic, 4–5.3 × 0.9–1.6 mm; petals elliptic, 2–4 × 1.2–1.5 mm, adnate to or free to androphore; nectary glands ovate, 0.5–0.8 × 0.3–0.6 mm, adnate to androphore, glabrous; stamens 7–8, staminodes 0. Pistillate flowers: sepals narrowly elliptic, 6–9 × 1.7–2.7 mm, without glands; petals 0 or 5, lanceolate, less than 0.5 mm; nectary glands ovate to oblong, 0.3–0.4 × 0.5–0.6 mm, glabrous; ovary strigose to hispidulous; styles 1.5–2.1 mm, glabrous; stigmas flattened. Capsules 3.5–9 mm, hispidulous. Seeds 3.5–4.2 mm, faintly and irregularly alveolate.
Phenology: Flowering Mar–Nov.
Habitat: Grasslands, oak woodlands, loamy to clayey, calcareous, often rocky, soils.
Elevation: 100–500 m.
Tex., Mexico (Coahuila).
Argythamnia simulans was described by Ingram as having staminate petals free from the androphore (Clemans 433, RSA), but in some specimens the staminate petals are adnate to the androphore (Riskind 2370 MEXU, TEX, DAV). This character is usually constant within a species, although it is in some instances difficult to discern. Further study is needed to determinate the significance of this variation within A. simulans.
In the flora area, Argythamnia simulans is found primarily on the Edwards Plateau.