5. Acleisanthes acutifolia Standley, Contr. U.S. Natl. Herb. 12: 370. 1909.
Plants herbaceous, overall pubescence mixture of capitate-glandular hairs 0.2-0.3 mm and white, capitate, shorter hairs 0.1-0.2 mm. Stems decumbent to ascending, much branched, 10-40 cm, hirtellous to glabrate. Leaves yellowish green, usually petiolate, distalmost sessile or nearly so, those of pair subequal; petiole 1-15 mm, puberulent to hirtellous; blade oval to oblong-elliptic, (5-)10-50 × 3-20(-25) mm, base acute to obtuse, margins crispate or undulate, apex apiculate and acute to obtuse or infrequently rounded; margins and adaxial midveins puberulent or occasionally hirtellous. Inflorescences solitary flowers, sessile or nearly so; bracts linear to subulate, 3-10 mm, hirtellous to puberulent. Flowers: chas-mogamous perianth 2-5 cm, puberulent, tube 1-1.5 mm diam., limbs 10-30 mm diam., stamens 5; cleistogamous perianth 4-10 mm, hirtellous, stamens 2(-5). Fruits with 5 narrow sulci and 5 broad, smooth ribs extending past glands, each bearing sticky, resinous gland in constriction below apex, ovate-oblong, constricted 0.5-1 mm below apex, 5-8 mm, base tapering, apex truncate, sparsely puberulent or glabrous.
Flowering spring-fall. Calcareous or gypseous soils in grasslands and shrublands; 700-2500 m; Tex.; Mexico (Chihuahua, Coahuila, Durango, Zacatecas).