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FNA | Family List | FNA Vol. 12 | Loasaceae

3b. MENTZELIA Linnaeus sect. BICUSPIDARIA S. Watson, Proc. Amer. Acad. Arts. 20: 367. 1885.

Joshua M. Brokaw

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.

Species 5 (5 in the flora): sw United States, nw Mexico.

SELECTED REFERENCE Daniels, G. S. 1970. The Floral Biology and Taxonomy of Mentzelia Section Bicuspidaria (Loasaceae). Ph.D. dissertation. University of California, Los Angeles.

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.   54 Mentzelia reflexa
+ 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 (1) Bracts conspicuous, concealing pedicels, ovaries, and capsules, white with green margins.   53 Mentzelia involucrata
+ Bracts inconspicuous, not concealing pedicels, ovaries, or capsules, green   (3)
3 (2) Stamen filament lobes 0.6–2.5 mm, anther stalk usually shorter; seeds constricted and grooved at middle.   55 Mentzelia tricuspis
+ Stamen filament lobes 0.1–0.7 mm, anther stalk equal or longer; seeds widest at middle, not grooved   (4)
4 (3) Petioles absent in cauline leaves, blade base often cordate-clasping; capsules erect; far southwestern Sonoran Desert.   52 Mentzelia hirsutissima
+ Petioles present in distalmost cauline leaves, blade base not cordate-clasping; proximal capsules nodding, distal erect; central Mojave Desert.   56 Mentzelia tridentata


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