Suffrutescent plants sometimes becoming subscandent, up to 60 cm. high or more; stems subquadrangular, glabrous or the upper portions more or less bifariously puberulous, the hairs up to 0.5 mm. long, retrorsely curved; leaf blades lanceolate to oblong-ovate or elliptic, up to 20 em. long and 5 cm. wide, shortly to slenderly acumi- nate, the tip often curved, obtuse or rounded at base or sometimes acute, moderately firm, entire or undulate, the upper surface glabrous or the costa and lateral veins (6 or 7 pairs) sparingly puberulous, the hairs subappressed, the lower surface likewise glabrous or sparingly puberulous on costa and veins, these more prominent than those of the upper surface, the cystoliths moderately conspicuous under a lens, up to 0.28 mm. long; petioles 3 to 8 mm. long, glabrous or sparingly puberulous; spikes terminal and axillary, the uppermost spike some- times forked or sparingly branched forming a loose panicle, slender, 3 to 12 cm. long, the peduncles slender, up to 7 cm. long, quadrangular, the angles faintly winged, glabrous or hirtellous, the hairs arranged more or less in two lines, up to 0.5 mm. long, the rachis slender, subquadrangular, more or less flattened near the nodes, moderately hirtellous; bracts lance-ovate, average size 4.5 mm. long, 2 mm. wide, acute or acuminate, rather firm, striate-veined (the costa and lateral veins prominent), moderately hirtellous, the hairs rigid, spreading, straight or slightly curved, up to 0.16 mm. long; bractlets subulate, 5.5 mm. long, 0.5 mm. wide, ciliate, otherwise glabrous except the costa, this prominent and sparingly hirtellous; calyx about 8 mm. long, hirtellous, the hairs up to 0.16 mm. long, more or less spreading, some of them eyathiform, the segments 4, subulate, 0.5 mm. wide at base, gradually narrowed to a slender filiform tip up to 3 mm. long; corollas red, reddish straw-color, dull crimson, violet or reddish orange, sparingly pubescent, the hairs up to 0.2 mm. long, more or less conspicuously septate, a few cyathiform hairs some- times smooth or minutely papillose.
Type in the U. S. National Herbarium, No. 1830660, collected at Villavicencio, Intendencia of Meta, Colombia, December 1928, by Brother Apollinaire "D."
Other collections are:

META: Cabuyaro, Sprague 12 (K). On boulders in stream bed, Caño Grande, near Villavicencio, 700 meters altitude, Jan. 22, 1939, Haught 2560 (US). Rich damp rocky woods along the Río Guatiquia, vicinity of Villavicencio, 350 meters altitude, Nov. 20, 1948, Araque-M. & Barkley 18M.018 (US). In primeval woods between Salitre and Upin, January 1876, André 1094 (K). Servita, 700 meters altitude, Triana, s.n. (K, NY). Villavicencio, Bro. Apollinaire "G" (US); "H" (US); "I" (US); "J" (US); 500 meters, Cuatrecasas 4518 (US); 4709 (US); moist situation in semishade, 1,600 feet altitude, February 7, 1948, Sandeman 5814 (K). Macizo Renjifo, Cordillera La Macarena, 1,300-1,900 m., Idrobo & Schultes 959 (US). NORTE DE SANTANDER: Valley of Río Margua, between Junín and Córdoba, 920 to 1,240 meters altitude, November 22, 1941, Cuatrecasas 13382 (US).
Justicia ischnorhachis can easily be recognized by its strongly nerved green bracts and slender spikes of flowers. The specific epithet is from the Greek laxvós, slender, and paxis, rachis.