Houstonia acerosa var. polypremoides (A. Gray) Terrell

Houstonia polypremoides A. Gray, Proc. Am. Acad. 21: 379
1886.
Houstonia polypremoides Bigelovii Greenman, Proc. Am. Acad. 32: 291. 1897.
Erect shrub, 1-2 dm. high, fruticose below, the stems usually very numerous and much branched, stout, minutely scaberulous or densely hirtellous, the internodes usually longer than the leaves, sometimes shorter; stipules about 0.5 mm. long, mostly bicuspidate; leaves opposite, sessile, the lowest linear-oblong, the upper ones acerose-linear, rigid, 5-12 mm. long, scaberulous or hirtellous, rarely glabrate, the margins revolute; flowers solitary, axillary and terminal, on stout pedicels 13 mm. long or shorter; hypanthium very short, scaberulous or hirtellous; calyxlobes lance-subulate, 3-4 mm. or rarely 1.5-2 mm. long, scaberulous, in fruit usually longer than the capsule; corolla salverform, white, 8-11 mm. long, the tube slender or stout, ampliate above, glabrous outside, the lobes oblong-ovate, about two thirds as long as the tube, obtuse or acutish, whitevillous within; capsule subglobose, 2.5-3 mm. long, broadly rounded or subretuse at the apex, densely hirtellous; seeds crateriform, with a short hilar ridge, black.
Type locality: Santa Eulalia Mountains, Chihuahua.
Distribution: Dry, rocky hillsides, western Texas, southern New Mexico, and Chihuahua.