Herbs or shrubby plants up to 2 meters high; stems subquadrangu- lar, upwardly strigose or glabrate, the hairs up to 0.25 mm. long; leaf blades ovate to oblong-ovate, up to 10 cm. long and 3 mm. wide, subacute to short-acuminate, narrowed at base, rather thin, entire or undulate, the upper surface nitid, glabrous to sparingly hirsute, the hairs up to 0.75 mm. long, ascending, the cystoliths rather promi- nent under a lens, about 0.08 mm. long, the lower surface pilosulous, the hairs confined chiefly to costa and veins (8 to 10 pairs), up to 0.2 mm. long, curved and ascending, the cystoliths prominent under a lens; petioles up to 2 mm. long, puberulous, the hairs appressed or ascending, up to 0.16 mm. long; flowers borne in loose terminal panicles up to 30 cm. long and 10 cm. broad, the branches slender, ascend- ing, few-flowered, the lower internodes of the inflorescence finely strigose or hirtellous, up to 4 cm. long, becoming shorter toward tip of panicle, the internodes of the ultimate branches about 1 cm. long and bearing in addition to the appressed hairs a few longer (0.75 mm.) more spreading ones, the lowermost branches of the inflorescence subtended by leaves similar but somewhat smaller than the main stem leaves, the upper branches of the inflorescence sub- tended by subulate bracts 2 to 3 mm. long and about 3 mm. wide at base, sparingly hirtellous; pedicels about 3 mm. long, minutely strigose or hirtellous; calyx deeply segmented, the segments linear, 7 to 10 mm. long and 1 mm. wide at base, gradually narrowed to an acute tip, minutely hirtellous, the hairs rigid, ascending, up to 0.16 mm. long; corolla bright red, 2.5 mm. long, glabrous, the tube 1 cm. long, 2.5 mm. wide at base, narrowed at 2 mm. above base to 1.5 mm., thence expanded to 5 mm. at mouth, the upper lip about 1 cm. long, 4 mm. wide at base, gradually narrowed to a blunt tip, usually more or less contorted, the lower lip more or less spreading, 1.5 mm. long, ovate, 8 mm. wide slightly below the middle, thence narrowed to 3 mm. at tip and terminated by 3 narrowly triangular lobes about 2.5 mm. long, the middle one 1.5 mm. wide at base, the lateral ones 1 mm. wide, all obtuse; stamens slightly exserted beyond the lower lip, the filaments glabrous and bright red, the anthers 3 mm. long and 0.5 mm. broad; ovary glabrous; capsules not seen.
Type in the U. S. National Herbarium, No. 1355119, collected in dense woods on the road from Pamplona to Toledo, crossing the divide between Río Teja (Maracaibo drainage) and Río Mesme (Orinoco drainage), Department of Norte de Santander, Colombia, 2,800 to 3,000 meters altitude, February 27-28, 1927, by E. P. Killip and Albert C. Smith (No. 19966). Isotypes: GH, NY.
The species is also represented by Killip and Smith's No. 20451, collected along stream in woods in the vicinity of Loso, north of Toledo, Department of Norte de Santander, 2,200 to 2,400 meters altitude, March 6-7, 1927 (GH, NY, US).
Habracanthus killipii is characterized by its rather thin and rela- tively small leaf blades, bright red corollas, and slenderly branched large lax panicles.