Cynanchum maccartii Shinners

Stems woody, not corky at base, glabrous. Leaves: 1 stipular col­leter on each side of petiole, sometimes with 1 additional interpetiolar colleter; petiole 2–5 mm, sparsely puberulent; blade linear-lanceolate, ellip­tic, or lanceolate, 10–30 × 2–8 mm, chartaceous, faintly pinnately veined, base rounded to cuneate, with 2 laminar colleters, margins planar, apex acute to rounded, mucronulate, surfaces glabrous abaxially, pilosulous on midvein adaxially, margins sometimes sparsely pilosulous. Inflorescences shortly racemiform, 3–8-flowered; peduncle 0–2 mm, puberulent. Pedicels 1–2 mm, glabrous. Flowers: calyx lobes lanceolate to ovate, apices obtuse to acute, 1–1.5 mm, margins scarious, with 1 colleter per sinus; corolla cream to yellowish cream, campanulate, tube 0.5 mm, lobes erect with spreading tips, opening not obscured, linear, 1.5–2 mm, abaxially glabrous, adaxially densely, short-puberulent marginally and apically with opaque, matted, flattened hairs, densely hispid centrally with downward-pointing acicular, translucent hairs; corona segments united to base of anthers, laminar, lanceolate, 1 mm, slightly longer than gynostegium; gynostegium sessile; style apex convex. Follicles dark brown, 4–7 × 0.4–0.7 cm, apically acuminate, glabrous. Seeds 8–12, brown, flat, 4–6 × 2–3 mm, winged, with minute papillae forming ridges, chalazal margin erose; coma white, 2–3 cm.

Flowering Apr–Oct; fruiting Jun–Oct. Valleys, plains, canyons, limestone, rocky, caliche, clay, or sandy soils, thorn scrub, oak-juniper woodland; 100–600 m; Tex.; Mexico (Coahuila, Nuevo León, Tamaulipas).

Metastelma palmeri overlaps in range with M. barbigerum in southern Texas. It is commonly encoun­tered in the blackbrush thorn scrub of the Rio Grande valley and southwestern margin of the Edwards Plateau.