Two-flowered or star milkvine

Gonolobus biflorus Rafinesque, New Fl. 4: 58. 1838; Chthamalia biflora (Rafinesque) Decaisne; G. biflorus var. wrightii A. Gray

Herbs. Stems 4–10, decumbent, often branched near base, 7–40 cm, hirsute with long eglandular and minute gland­ular trichomes. Leaves 1 or 2 colleters on each side of petiole; petiole 0.5–2.5 cm, hirsute with long eglandular and minute glandular tri­chomes; blade ovate to deltate, 0.8–5 × 0.6–3.2 cm, base shallowly to deeply cordate, with 0–2 laminar colleters, apex acute (rounded), surfaces hirsute with long eglandular and minute glandular trichomes, espe­cially so on veins abaxially. Inflorescences solitary, umbelliform, extra-axillary, sessile or subsessile, 1–2-flowered. Pedicels 3–11 mm, hirsute with long eglan­dular and minute glandular trichomes. Flowers: calyx lobes spreading, oval to ovate, 1.8–2.5 mm, apex rounded or acute, hirsute with long eglandular and minute glandular trichomes; corolla maroon to dark brown, not reticulate, rotate-campanulate, tube 1–1.5 mm, lobes spreading, ovate to narrowly deltate to spatulate, 3–6 mm, margins usually reflexed, pilose to hirsute adaxially; corona united to corolla and column near base, composed of 5 united segments forming a ring at base, each with an adaxial incurved appendage arching above or incumbent on anthers, equaling or exceeding style apex, maroon to dark brown, 1–1.5 mm, glabrous; apical anther appendages white, maroon to brown at base, broadly deltoid; style apex rounded, flat. Follicles not striate, ellipsoid to ovoid, 4.5–8.5 × 1.8–3.5 cm, apex acute, densely muricate (more than 1 protrusion per cm of length), villous to hirsute with long eglandular and minute glandular trichomes. Seeds tan to light brown, oval to nearly orbicular or ovate, 8–11 × 7–10 mm, margins broadly winged, chalazal end erose, faces minutely rugose; coma 2.5–4 cm.

Flowering Mar–Oct; fruiting Apr–Dec. Calcareous prairies, hillsides, pastures, fields, savannas; 100–1300 m; N.Mex., Okla., Tex.

Matelea biflora is occasionally found in grasslands and savannas of the southern Great Plains. It is most common on and around the Edwards Plateau of cen­tral Texas, where it occurs in grass-dominated habitats including disturbed areas. The range extends mostly northward and westward of that region to central Oklahoma and extreme eastern New Mexico (Lea County), where the species is much less common. Its conservation status in New Mexico merits evaluation. The plants are covered in short, glandular hairs and are malodorous when touched. The flowers occur most often in pairs, hence the common name two-flowered milkvine.