Slender herbs up to 30 cm. high; stems erect or ascending, simple or sparingly branched forming dense clumps, sharply quadrangular or the angles narrowly winged, glabrous or sparingly hirtellous at the nodes, these more or less swollen, the basal portion of the stems 1 to 1.5 mm. in diameter; leaf blades linear-lanceolate, up to 5 cm. long and 1.5 to 4.5 mm. wide, gradually narrowed to an obtuse tip and into a slender base, glabrous except the costa (prominent) and lateral veins (4 or 5 pairs, obscure), these sparingly hirtellous, the margins of the leaves sometimes sparingly ciliolate, the cystoliths usually small, scattered and inconspicuous; interpetiolar hairs whitish, up to 0.64 mm. long, flattened, septate; flowers axillary, solitary or several in a cluster, the pedicels up to 3 cm. long, flattened, narrowly winged; bracts subtending the pedicels lanceolate, 5 mm. long, 0.5 mm. wide, acute to obtuse, glabrous, the costa and margins whitish, the costa sparingly hirtellous and the margins sparingly ciliolate with hairs. about 0.2 mm. long; calyx 5 mm. long, the tube glabrous, the segments linear, about 5 mm. long, subcarinate, glabrous or sparingly hirtellous and ciliate, the hairs ascending, about 0.2 mm. long; corolla white or lilac, 7 mm. long, puberulous, the lobes ovate, 1.5 mm. long and 1.25 mm. wide, rounded at tip; stamens included, the longer pair 3.5 mm. long, the shorter 1.5 mm. long, the anthers linear, 1 mm. long, 0.25 mm. broad; capsules linear, 10 mm. long, 1.25 mm. broad, 0.75 mm. thick, obtuse and apiculate, glabrous; retinacula 0.35 mm. long, acute; seed usually 16 in each capsule, brown, flattened, ca. 1 mm. long, 0.6 mm. wide, 0.25 mm. thick, rounded at tip, oblique at base, glabrous when dry but mucilaginous-pilose when moistened.

Naya, between Puerto Merizalde and Meregildo, Cuatrecasas 14346 (US). Wet rocky soil on edge of Río Sabaletas, at Sabaletas, km. 29 of highway from Buena- ventura to Cali, Killip & Cuatrecasas 38856 (US).

The specimens cited were all collected at low altitudes (5 to 80 meters). The plants, often forming dense clumps, are of a bright green color. Killip states that it is a characteristic plant along the Río San Juan. The species is unique in the genus Hygrophila because of its small size, hence its name from the Greek.