Herb up to 0.5 meter high; stems quadrangular, the angles sharp or the lower portions subquadrangular, pilose to subtomentose, the hairs appressed, whitish, up to 0.5 mm. long; leaf blades ovate to oblong-ovate, up to 13 cm. long and 6 cm. wide, short-acuminate (the tip itself obtuse), cuneate at base, rather firm, undulate or crenate- serrate, the upper surface glabrous or bearing a few scattered hairs, the lower surface sparingly to rather densely pilose, especially the costa and lateral veins (about 10 pairs), the hairs appressed to ascend- ing, up to 0.16 mm. long, the venation prominent beneath, less so above, the cystoliths rather obscure, up to 0.112 mm. long; petioles up to 4 cm. long, appressed-pilose, the hairs similar to those on the stems; flowers borne in terminal spikes up to 7 cm. long and 3 cm. broad, the bracts and bractlets conspicuous, lanceolate, moderately pilose and ciliate, the hairs up to 1.25 mm. long, ascending, the bracts 2 cm. long and 0.5 mm. wide or the lowermost larger, the bractlets 1.5 cm. long and 2.25 mm. wide, both bracts and bractlets subacute to subobtuse; calyx about 14 mm. long, the segments linear, about 12 mm. long and 0.75 mm. wide, gradually narrowed to a blunt tip, ciliate and sparingly pilose, the hairs spreading or ascending, up to 1.25 mm. long, the costa prominent; corolla 3.5 cm. long, white, mi- nutely pubescent, the tube 2.5 mm. in diameter, expanding from about the middle to 8 mm. at throat, the lobes suborbicular, about 7 mm. in diameter; stamens reaching or slightly exceeding the mouth of the corolla, the filaments glabrous except toward the puberulous base, the anthers linear, 3 mm, long, 0.5 mm. wide; capsules 14 mm. long, clavate, 4 to 5 mm. broad, 3 mm. thick, rather densely pubescent, the hairs up to 0.16 mm. long, ascending or spreading at and near tip, retrorse toward base, the retinacula nearly straight, 4 mm. long and 0.5 mm. wide near base, acute to rounded and more or less fimbri- ate at tip; seed brown, about 3 mm. long and 2.5 mm. wide and 0.5 mm. thick, mucilaginous-tomentose when moistened.
Type in the U. S. National Herbarium, No. 2045435, collected on creek bank in subtropical forest in the Quebrada Playón, in the Río Manzanares Valley, 20 km. west of La Esperanza and 42 km. west of Villavicencio, Cordillera Oriental, Intendencia of Meta, Colombia,
1,200 meters altitude, August 29, 1944, by Martin L. Grant (No. 10013). Isotype: US, 2107000.
Ruellia grantii should be easy to recognize in the field by its stiff habit, square stems and largish spikes with conspicuous narrow bracts and bractlets, and by the white, puberulous corollas.