Mentzelia obscura |
Mentzelia shultziorum |
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Pacific blazing star |
Shultz's blazingstar |
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Habit | Plants candelabra-form, 8–45 cm. | Plants perennial, bushlike, with subterranean caudices. |
Stems | multiple, erect or decumbent, zigzag; branches along entire stem, distal longest, antrorse, straight to upcurved; hairy. |
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Leaves | blade 13.6–33.3 × 7.2–18.5 mm, widest intersinus distance 6.2–14.8 mm; proximal elliptic, margins dentate, teeth 4–6, perpendicular to leaf axis, 0.5–0.6 × 1.2–1.5 mm; distal oblanceolate to elliptic, base usually not clasping, rarely clasping, margins dentate to serrate, teeth 4–8, slightly antrorse or perpendicular to leaf axis, 0.6–2.5 mm; abaxial surface with simple grappling-hook and complex grappling-hook trichomes, adaxial surface with simple grappling-hook and needlelike trichomes. |
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Basal leaves | persisting; petiole present or absent; blade linear-lanceolate to linear, margins usually irregularly deeply lobed, lobes pointed. |
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Cauline leaves | petiole absent; blade ovate-lanceolate to linear, to 15(–22) cm, margins few-lobed or entire. |
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Bracts | green, ovate to ovate-lanceolate, 2.9–8.2 × 1.1–1.9 mm, width 1/8–1/2 length, not concealing capsule, margins entire. |
margins entire or slightly toothed. |
Flowers | sepals 2–6 mm; petals yellow to orange proximally, yellow distally, 3–8 mm, apex rounded or acute apex; stamens 20–40, 2–7 mm, filaments monomorphic, filiform, unlobed; styles 2–6 mm. |
petals golden yellow, 7.7–14.8 × 2.7–5.9 mm, apex acute, glabrous abaxially; stamens golden yellow, 5 outermost petaloid, filaments narrowly spatulate, strongly clawed, 6–11 × 1.9–5.2 mm, with anthers, second whorl with anthers; anthers straight after dehiscence, epidermis smooth; styles 5.4–9.7 mm. |
Capsules | clavate, 11–31 × 1.5–3 mm, axillary curved to 250° at maturity, usually inconspicuously longitudinally ribbed. |
cup-shaped, 4.2–8 × 4.9–7.6 mm, base rounded, not longitudinally ridged. |
Seeds | 15–50, in 2+ rows distal to mid fruit, tan, usually not, occasionally sparsely, dark-mottled, usually irregularly polygonal, occasionally triangular prisms proximal to mid fruit, surface colliculate under 10x magnification; recurved flap over hilum absent; seed coat cell outer periclinal wall domed, domes on seed edges less than 1/2 as tall as wide at maturity. |
coat anticlinal cell walls straight, papillae 4–6 per cell. |
2n | = 36. |
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Mentzelia obscura |
Mentzelia shultziorum |
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Phenology | Flowering Feb–May. | Flowering Aug–Sep. |
Habitat | Sandy to rocky washes or slopes, desert scrub, Joshua-tree woodlands, roadsides. | Steep, barren slopes of white, green, and red clayey soils. |
Elevation | 200–1700 m. (700–5600 ft.) | 1200–1600 m. (3900–5200 ft.) |
Distribution |
AZ; CA; NV; UT; Mexico (Baja California, Sonora)
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UT |
Discussion | Mentzelia obscura is morphologically intermediate to M. desertorum and M. albicaulis and is known to occur in mixed populations with both species. Reliable discrimination among these species usually requires mature seeds. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Mentzelia shultziorum occurs only on outcrops above Onion Creek and at the head of Castle Valley in Grand County. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 540. | FNA vol. 12, p. 513. |
Parent taxa | Loasaceae > Mentzelia > sect. Trachyphytum | Loasaceae > Mentzelia > sect. Bartonia |
Sibling taxa | ||
Name authority | H. J. Thompson & J. E. Roberts: Phytologia 21: 284. (1971) | Prigge: Great Basin Naturalist 46: 361, figs. 1, 3, 4. (1986) |
Web links |