Mentzelia obscura |
Mentzelia librina |
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Pacific blazing star |
Book Cliffs stickleaf |
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Habit | Plants candelabra-form, 8–45 cm. | Plants perennial, bushlike, with subterranean caudices or rhizomes. |
Stems | multiple, erect, zigzag; branches distal or along entire stem, distal longest or all ± equal, antrorse, straight to upcurved; hairy. |
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Leaves | blade 14–26.3 × 5.1–10.8 mm, widest intersinus distance 2.3–5.2 mm; proximal oblanceolate to elliptic, margins usually 3-fid, rarely entire or pinnate, teeth or lobes usually 2, rarely 0 or 4, perpendicular to leaf axis, 0.8–2.7 mm; distal elliptic, base not clasping, margins 3-fid to occasionally pinnate, teeth or lobes usually 2, occasionally 4, perpendicular to leaf axis, 1.5–3.5 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 usually entire, rarely pinnate. |
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, 8.3–13.6 × 2.6–4.8(–6.2) mm, apex acute, glabrous abaxially; stamens golden yellow, 5 outermost petaloid, filaments broadly spatulate, strongly clawed, 6–8(–9.1) × 2.3–4.4 mm, with anthers, second whorl with anthers; anthers straight after dehiscence, epidermis smooth; styles 5–7.9 mm. |
Capsules | clavate, 11–31 × 1.5–3 mm, axillary curved to 250° at maturity, usually inconspicuously longitudinally ribbed. |
cup-shaped, 4–7.3 × 3.3–5.8 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 4–5 per cell. |
2n | = 36. |
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Mentzelia obscura |
Mentzelia librina |
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Phenology | Flowering Feb–May. | Flowering Jun–Sep. |
Habitat | Sandy to rocky washes or slopes, desert scrub, Joshua-tree woodlands, roadsides. | Barren gray soils, steep shale slopes. |
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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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 librina in narrowly distributed along the border between Carbon and Emery counties. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 540. | FNA vol. 12, p. 511. |
Parent taxa | Loasaceae > Mentzelia > sect. Trachyphytum | Loasaceae > Mentzelia > sect. Bartonia |
Sibling taxa | ||
Synonyms | M. multicaulis var. librina | |
Name authority | H. J. Thompson & J. E. Roberts: Phytologia 21: 284. (1971) | (K. H. Thorne & F. J. Smith) J. J. Schenk & L. Hufford: Novon 19: 119. (2009) |
Web links |