Mentzelia obscura |
Mentzelia rhizomata |
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Pacific blazing star |
Roan Cliffs blazingstar |
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Habit | Plants candelabra-form, 8–45 cm. | Plants perennial, bushlike, with rhizomes. |
Stems | multiple, erect or decumbent, zigzag; branches along entire stem, distal longest, antrorse, upcurved; hairy. |
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Leaves | blade 8.1–29 × 4.1–12.7 mm, widest intersinus distance 4.1–7.4 mm; proximal oblanceolate, margins entire; distal elliptic, base not clasping, margins entire or dentate, teeth 0–8, perpendicular to leaf axis, 0.6–2.7 mm; abaxial surface with simple grappling-hook and needlelike trichomes, adaxial surface with 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. |
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, 12.5–17.2 × 6.1–11.2 mm, apex rounded to obtuse, glabrous abaxially; stamens golden yellow, 5 outermost petaloid, filaments narrowly spatulate, strongly clawed, 7–9.5 × 2.7–6 mm, with anthers, second whorl with anthers; anthers straight after dehiscence, epidermis smooth; styles 7–10 mm. |
Capsules | clavate, 11–31 × 1.5–3 mm, axillary curved to 250° at maturity, usually inconspicuously longitudinally ribbed. |
cup-shaped, 7–10 × 6.5–8 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 9–13 per cell. |
2n | = 36. |
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Mentzelia obscura |
Mentzelia rhizomata |
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Phenology | Flowering Feb–May. | Flowering Jul–Aug. |
Habitat | Sandy to rocky washes or slopes, desert scrub, Joshua-tree woodlands, roadsides. | Sparsely vegetated, steep talus slopes with loose gravelly soils. |
Elevation | 200–1700 m. (700–5600 ft.) | 1700–2100 m. (5600–6900 ft.) |
Distribution |
AZ; CA; NV; UT; Mexico (Baja California, Sonora)
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CO |
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 rhizomata is known only from Garfield 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 | ||
Synonyms | Nuttallia rhizomata | |
Name authority | H. J. Thompson & J. E. Roberts: Phytologia 21: 284. (1971) | Reveal: Syst. Bot. 27: 763, figs. 1, 2. (2002) |
Web links |