Mentzelia obscura |
Mentzelia torreyi |
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Pacific blazing star |
Torrey's blazing star |
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Habit | Plants candelabra-form, 8–45 cm. | Plants with ground-level or subterranean caudices. | ||||
Stems | 5–25 cm. |
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Leaves | petiole absent; blade ovate or obovate, to 45 × 35 mm, intersinus distance 2–4 mm. |
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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. |
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Pedicels | 0(–1.5) mm. |
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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 yellow to orange, narrowly spatulate to obovate, 4.5–17 × 1.2–5 mm, apex rounded; stamens 25–45, 7–21 mm; styles 7–18 mm. |
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Capsules | clavate, 11–31 × 1.5–3 mm, axillary curved to 250° at maturity, usually inconspicuously longitudinally ribbed. |
3–7 × 3–4.5 mm. |
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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. |
3–9 per capsule, edges prominently to inconspicuously ridged. |
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2n | = 36. |
= 28. |
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Mentzelia obscura |
Mentzelia torreyi |
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Phenology | Flowering Feb–May. | |||||
Habitat | Sandy to rocky washes or slopes, desert scrub, Joshua-tree woodlands, roadsides. | |||||
Elevation | 200–1700 m. (700–5600 ft.) | |||||
Distribution |
AZ; CA; NV; UT; Mexico (Baja California, Sonora)
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CA; ID; NV
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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.) |
Varieties 2 (2 in flora). In the phylogenetic study by L. Hufford et al. (2003), Mentzelia torreyi was recovered as the sister to the rest of the genus. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 12, p. 540. | FNA vol. 12, p. 530. | ||||
Parent taxa | Loasaceae > Mentzelia > sect. Trachyphytum | Loasaceae > Mentzelia > sect. Micromentzelia | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Name authority | H. J. Thompson & J. E. Roberts: Phytologia 21: 284. (1971) | A. Gray: Proc. Amer. Acad. Arts 10: 72. (1874) | ||||
Web links |