2a. Mentzelia humilis (Urban & Gilg) J. Darlington var. humilis
Gypsum blazingstar Gypsum blazingstar
Nuttallia gypsea Wooton & Standley
Leaf blades: widest intersinus distance 0.8–2.6(–3.3) mm; proximal oblanceolate to elliptic, margins pinnatisect, lobes 4–16(–20), 2.3–11.8(–16.4) × 1–2.9 mm; distal elliptic, lanceolate, or linear, margins entire, dentate, or pinnatisect, teeth or lobes (0–)4–16, 2.3–13.8(–16.9) × 0.9–1.8 mm. Flowers: petals 11.8–21.3(–24.6) × 1.4–3.7 mm; 5 outermost stamens linear to narrowly spatulate, 10.6–19(–22.3) × 0.7–3.3 mm. Seed coat: papillae 7–12 per cell. 2n = 20.
Flowering Apr–Oct. Sparsely vegetated areas in dry grasslands, roadsides, level areas or gentle slopes, gravelly, clayey, and sandy gypsum substrates; 900–1600 m; N.Mex., Tex.
Variety humilis occurs in western Texas and south-central New Mexico. Its range approaches Mentzelia humilis var. guadalupensis in Eddy County, New Mexico, but the two varieties are not known to co-occur.