Gomphocarpus rivularis Schltr.

Perennial rheophytic herb to c.1.2 m tall, roots thick, white, fleshy; stems erect, with several unbranched glabrous stems from base. Leaves in whorls of 3 or 4, petiole 3-10 mm long, interpetiolar ridges present, frequently with several colleters; lamina 7-12 x 0.5-1 cm, linear-lanceolate, apex attenuate, base cuneate, margins smooth, glabrous. Inflorescences extra-axillary with 8-16(-24) flowers in a nodding umbel; peduncles 2-5 cm long, slender, ascending, glabrous; bracts deciduous; pedicels 1.5-3 cm long, slender, flexuous, glabrous. Sepals 2.5-4 x 1-1.8 mm, lanceolate to ovate, acute, glabrous. Corolla reflexed, exposed (adaxial) face white, glabrous or minutely papillose except for the somewhat bearded margins, abaxial face generally tinged with pink, glabrous; lobes 4-6 x 2-3 mm, oblong to ovate, subacute. Corona lobes attached ±1 mm above the base of staminal column, cucullate, not compressed laterally, 2 x 2 mm, ± as tall as column, the upper margin level, rounded distally and proximal angles forming a pair of rounded lobules, lacking any form of tooth within the cavity, white. Anther wings 1.5 mm long, triangular. Corpusculum c.0.4 x 0.15 mm, ovoid-subcylindrical, brown; translator arms c.0.3 mm long, flattened, geniculate; pollinia c.1.2 x 0.4-0.5 mm, flattened, oblong-subtriangular in outline. Stigma head flat. Fruiting pedicel straight, nodding slightly; follicles 2-3(-4) x 1-2.5 cm, ovoid-subglobose, somewhat inflated, apical beak extremely short or absent, glabrous, smooth or with a few filiform processes to c.4 mm long. Seeds 5-6 x 3-4 mm, flattened on one face, the other convex, ovate, smooth and with a wrinkled and inflated rim c.1 mm wide; coma of silky hairs c.5 mm long.