Suffrutescent plants up to 30 cm. high or more; stems subquadrangu- lar, hirtellous in two lines (the hairs about 0.25 mm. long), the lower portions glabrate, the cystoliths subpunctiform; leaves subsessile, the blades lanceolate, up to 10 cm. long and 2.5 cm. wide, acuminate (the tip itself blunt), narrowed from about middle to a subauriculate base, entire or undulate, subchartaceous, the upper surface glabrous, the lower surface glabrous or minutely and sparingly hispidulous (the hairs about 100 long), the cystoliths appearing black, the costa and lateral veins (7 or 8 pairs) rather prominent; petioles about 1 mm. long; flowers borne in terminal racemes up to 7 cm. long, the peduncles up to 3 cm. long, puberulous in two lines, the rachis puberulous, the hairs about 0.25 mm. long, some of them gland-tipped, the pedicels slender, the lowermost up to 8 mm. long, successively shorter toward tip, all puberulous with both glandular and eglandular hairs; bracts narrowly triangular, the largest and lowermost up to 1 cm, long and 3 mm. wide at base, narrowed to an obtuse tip, bractlets similar but about half as large, both bracts and bractlets glabrous or sparingly puberulous, sometimes bearing a few additional glandular hairs; calyx 6 mm. long, the segments linear-lanceolate, 5 mm. long, 1 mm. wide at base, acute, ending in a blunt tip, puberulous, the pubescence a mixture of glandular and eglandular hairs up to 150μ long; corolla white or purple(?), about 15 mm. long, the tube about 2 mm. broad at base, gradually expanded to 8 mm. at mouth, somewhat curved and ventricose, minutely and sparingly pubescent, the lobes ovate, about 6 mm. long and 4 mm. wide; stamens 4 mm. long, attached at 5 mm. above base of corolla, the anthers 2 mm. long, the staminodes 1 mm. long, both stamens and staminodes glabrous; capsules clavate, 21 mm. long, puberulous, 4-seeded, the solid basal portion about 6 mm. long and 3 mm. broad, the tip blunt, the seed-bearing cavity 4 mm. broad, the seed flattened, about 3.5 mm. long and 3 mm. broad, verrucose, the retinacula linear, curved, about 3 mm. long, thin and acute at tip. Type in the herbarium of the Facultad de Agronomía, Medellín, Colombia, No. 1905, collected at Támesis, Department of Antioquia, Colombia, February 1, 1928, by Rafael A. Toro (No. 943). Pseuderanthemum leiophyllum is well marked and has no close re- semblance to any other Colombian species. The color of the corolla is not apparent in the herbarium material. The name leiophyllum is derived from Xeios, smooth, and púλov, leaf.