3. Ruellia potamophila Leonard, sp. nov. FIGURE 26 Suffrutex, caulibus subquadrangularibus, glabris, nodis tumidis, perspicue cystolithigeris; lamina foliorum oblongo-ovata, apice acuminata, basi angustata, integra vel leviter crenata; pedunculi sub- teretes, dichotomo-ramosi, glabri, parce et minute pubescentes; brac- teae infimae foliosae, supremae parvae, spathulatae vel lineares ; pedi- celli parce pubescentes vel glabrati; calycis segmenta subulata; corolla alba, glabra, hypocrateriformis, leviter ventricosa, lobis ovatis, ro- tundatis vel emarginatis; capsulae clavatae, glabrae, stipite gracili. Suffrutescent herbs up to 2 meters high; stems subquadrangular, glabrous, the nodes swollen, the cystoliths numerous and conspicuous; leaf blades oblong-ovate, up to 18 cm. long and 6.5 cm. wide, acuminate, narrowed at base, glabrous, entire or shallowy crenate, the costa and lateral veins (8 pairs) rather prominent, the cystoliths prominent; petioles up to 2 cm, long; flowers borne in lax dichotomously branched cymes, the peduncles up to 8 cm. long, subterete, the primary branches 3 to 4 cm. long, the others relatively shorter, all terete and, like the peduncles, glabrous or sparingly and minutely pubescent, the hairs spreading; lower bracts leaflike, deciduous in some plants, the upper- most bracts spathulate or linear, 5 to 10 mm. long; pedicels 2 to 10 mm. long, minutely and sparingly pubescent or glabrate; calyx 7 to 10 mm. long, glabrous, the segments subulate; corolla white, 28 mm, long, glabrous, the lower half slender, 2 mm. in diameter, the upper half funnelform, slightly ventricose, 8 mm. broad at mouth, the lobes ovate, 6 to 8 mm. long, 3 to 5 mm. wide, rounded or shallowly emarginate, the stamens included; capsules 2 cm. long, glabrous, the stipe slender, 8 to 9 mm. long, the seed-bearing portion oval, 5 mm. broad, 4-seeded, pointed.
Type in the U. S. National Herbarium, No. 1771543, collected in dense forest along the Río Engaña, Río Digua Valley, Department of El Valle, Colombia, 675 meters altitude, April 2 to 4, 1939, by E. P. Killip (No. 34747). Also represented by: CALDAS: Santa Cecilia, 800 meters altitude, von Sneidern 5075 (Ch). EL VALLE: Woods at Piedra de Moler, on the left bank of the Río Digua, 900 to 1,180 meters, Cuatrecasas 15035 (US). Below Queremal, along the Río San Juan, 1,300 to 1,500 meters altitude, Cuatrecasas 23947 (US). Ruellia potamophila is related in a general way to R. macrophylla, but it is distinguishable by its white flowers, subulate calyx segments, and narrowly winged ciliate peduncles. The name potamophila (Torauós, river, and pixée, loving) alludes to the plant's predilec- tion for growing on banks of streams and rivers. It is usually found in densely wooded regions.