Mentzelia obscura |
Mentzelia collomiae |
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Pacific blazing star |
Sunset Crater blazingstar |
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Habit | Plants candelabra-form, 8–45 cm. | Plants biennial, candelabra-form. |
Stems | solitary, erect, straight; branches distal, distal longest, antrorse, straight; hairy. |
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Leaves | blade 17.8–55.2 × 3–16.6(–26.3) mm, widest intersinus distance 1.4–4.9 mm; proximal oblanceolate, lanceolate, or elliptic, margins dentate to pinnate, teeth or lobes 8–18, perpendicular to leaf axis, 0.6–5.3 mm; distal elliptic to lanceolate, base not clasping, margins dentate to pinnate, teeth or lobes 4–12, perpendicular to leaf axis, 0.7–6.8 mm; abaxial surface with simple grappling-hook, complex grappling-hook, and needlelike 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 usually entire, occasionally 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, 8.5–16.2 × 2.6–6.4 mm, apex acute to rounded, glabrous abaxially; stamens golden yellow, 5 outermost petaloid, filaments narrowly spatulate, strongly clawed, (6–)9.9–13.8 × (1–)2.4–4.3 mm, without anthers, second whorl with anthers; anthers straight after dehiscence, epidermis smooth; styles (5–)7.8–11 mm. |
Capsules | clavate, 11–31 × 1.5–3 mm, axillary curved to 250° at maturity, usually inconspicuously longitudinally ribbed. |
cylindric, 9.3–16.1 × 3.6–5.9 mm, base tapering, 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 sinuous, papillae 51–59 per cell. |
2n | = 36. |
= 22. |
Mentzelia obscura |
Mentzelia collomiae |
|
Phenology | Flowering Feb–May. | Flowering Jun–Aug. |
Habitat | Sandy to rocky washes or slopes, desert scrub, Joshua-tree woodlands, roadsides. | Sparsely vegetated level ground, slopes, black (to sometimes reddish) volcanic cinder cone soils. |
Elevation | 200–1700 m. (700–5600 ft.) | 1300–2500 m. (4300–8200 ft.) |
Distribution |
AZ; CA; NV; UT; Mexico (Baja California, Sonora)
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AZ |
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 collomiae is known only from the San Francisco Volcanic Field of Coconino County. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 540. | FNA vol. 12, p. 519. |
Parent taxa | Loasaceae > Mentzelia > sect. Trachyphytum | Loasaceae > Mentzelia > sect. Bartonia |
Sibling taxa | ||
Name authority | H. J. Thompson & J. E. Roberts: Phytologia 21: 284. (1971) | Christy: Novon 7: 25. (1997) |
Web links |