Straggling moderately branched perennial; stems up to 1.5 m. long, though generally less, often reddish tinged, rooting at the lower nodes, becoming somewhat woody towards the base, 8–9 mm. in diameter, finely pubescent when young but eventually glabrescent.. Leaves opposite or in verticils of 3, often some alternate on the same stem; petiole 1–8 cm. long; lamina ovate to narrowly elliptical, 3–13 cm. long, 1.5–7 cm. broad, the base rounded or somewhat attenuate, the apex acuminate, pubescent on both surfaces, more densely so when young; lateral veins (5–)8–16 pairs; margin crenate-dentate, with several ± 1–2 mm. long fimbriae at the base of the lamina.. Inflorescence a (1–)2–5-flowered subumbellate raceme; flowers bright pink or mauve.. Peduncle 1.7–9 cm. long, pubescent.. Bracts ovate-lanceolate, 7–9 mm. long, acute to acuminate, pubescent, caducous.. Pedicels (0.5–)1–3 cm. long, slender, pubescent.. Lateral sepals ovate, 7–9 mm. long, 3–6 mm. broad, apiculate, pubescent.. Lower sepal navicular, 14–17 mm. long, 6–7 mm. deep, abruptly constricted into a 20–45 mm. long curved filiform spur, ± pubescent.. Dorsal petal 7–12 mm. long, 4–6 mm. broad, semicucullate, ± pubescent along the dorsal crest and towards the base.. Lateral united petals 20–35 mm. long; upper petal lanceolate-oblong, 10–13 mm. long, 5–6 mm. broad; lower petal oval, 17–31 mm. long, 12–22 mm. broad, distally with a slight emargination along the inner margin.. Ovary glabrous.. Fruit fusiform, ± 13 mm. long and 5 mm. broad, glabrous.. Fig. 4/41, p. 8