Herbs, annual. Leaves: basal rosette present, not persistent, proximalmost internodes to 10+ mm; blade without broad basal lobes, margins toothed to pinnate, flat. Flowers: stamens all fertile or 1–3(–5) outermost sterile, filaments dorsiventrally flattened, ±monomorphic, linear, or heteromorphic, 1–3(–5) outermost oblanceolate, petaloid, inner linear, distally 2-lobed or unlobed; ovules (and seeds) oriented perpendicular or ± parallel to long axis of ovary. Capsules cup-shaped, cylindric, or ovoid, straight. Seeds pyriform to ovoid and flattened dorsiventrally, not winged; seed coat cells polygonal, ± isodiametric, anticlinal walls straight or wavy.

Distribution

sw United States, nw Mexico.

Discussion

Species 5 (5 in the flora).

Selected References

None.

Lower Taxa

Mentzelia hirsutissima, Mentzelia involucrata, Mentzelia reflexa, Mentzelia tricuspis, Mentzelia tridentata

Key

1	1–3(–5) outermost stamens staminodial and petaloid (flowers appearing to have 6–8(–10) petals); stamen filaments unlobed; petals lanceolate to oblanceolate, 6–12 mm, apices acute; styles 5–6.5 mm.	Mentzelia reflexa
1	Stamens all fertile, none petaloid (flowers appearing to have 5 petals); stamen filaments all or most distally 2-lobed; petals obovate, 10–65 mm, apices mucronate; styles 6–30 mm.	> 2
2	Bracts conspicuous, concealing pedicels, ovaries, and capsules, white with green margins.	Mentzelia involucrata
2	Bracts inconspicuous, not concealing pedicels, ovaries, or capsules, green.	> 3
3	Stamen filament lobes 0.6–2.5 mm, anther stalk usually shorter; seeds constricted and grooved at middle.	Mentzelia tricuspis
3	Stamen filament lobes 0.1–0.7 mm, anther stalk equal or longer; seeds widest at middle, not grooved.	> 4
4	Petioles absent in cauline leaves, blade base often cordate-clasping; capsules erect; far southwestern Sonoran Desert.	Mentzelia hirsutissima
4	Petioles present in distalmost cauline leaves, blade base not cordate-clasping; proximal capsules nodding, distal erect; central Mojave Desert.	Mentzelia tridentata