Mentzelia mollis

Plants candelabra-form, 3–15(–20) cm. Basal leaves not persisting. Cauline leaves: petiole present (proximal leaves), absent (distal leaves); blade lanceolate to linear (proximal leaves), ovate to lanceolate (distal leaves), to 6 cm, margins dentate or entire (proximal leaves), entire (distal leaves). Bracts green, ovate to elliptic, 5–8.5 × 2–5 mm, width 2/5–3/5 length, not concealing capsule, margins entire. Flowers: sepals 3–5.5 mm; petals yellow to orange proximally, yellow distally, 8–12 mm, apex rounded; stamens 20+, 3–8 mm, filaments monomorphic, filiform, unlobed; styles 7–9 mm. Capsules cylindric or clavate, 5–22 × 2–4 mm, axillary curved to 45° at maturity, often prominently longitudinally ribbed. Seeds 15–25, in 2+ rows distal to mid fruit, tan, dark-mottled, irregularly polygonal, surface smooth to minutely tessellate under 10× magnification; recurved flap over hilum absent; seed coat cell outer periclinal wall flat to slightly convex. 2n = 36.

Phenology: Flowering Apr–Jul.
Habitat: Barren, sodic or calcic clay slopes and bluffs derived from volcanic ash.
Elevation: 800–1500 m.

Idaho, Nev., Oreg.

Discussion

Mentzelia mollis is narrowly distributed in eastern Malheur County, Oregon, and western Owyhee County, Idaho, and disjunctly in the Black Rock Range of Humboldt County, Nevada. Recent phylogenetic studies support treatment of these disjunct populations as a single species (J. M. Brokaw and L. Hufford 2010b). In both ranges, M. mollis is predominantly limited to barren soils with high salinity. Mentzelia mollis is listed as endangered by the Oregon Department of Agriculture and is in the Center for Plant Conservation’s National Collection of Endangered Plants.

Selected References

None.

Lower Taxa