Mentzelia obscura |
Mentzelia dispersa |
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Pacific blazing star |
bushy blazing-star, bushy mentzelia, Nada stickleaf, Nevada blazingstar, scattered blazing star |
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Habit | Plants candelabra-form, 8–45 cm. | Plants wandlike or candelabra-form, 10–40(–50) cm. |
Basal leaves | persisting; petiole present or absent; blade linear-lanceolate to linear, margins usually irregularly deeply lobed, lobes pointed. |
persisting; petiole present or absent; blade elliptic to linear, margins usually dentate, sinuses extending less than 1/4 to midvein, or entire, rarely deeply lobed. |
Cauline leaves | petiole absent; blade ovate-lanceolate to linear, to 15(–22) cm, margins few-lobed or entire. |
petiole present or absent (proximal leaves), absent (distal leaves); blade elliptic to linear (proximal leaves), orbiculate to linear (distal leaves), to 10 cm, margins usually dentate, sinuses extending less than 1/4 to midvein, or entire, rarely deeply lobed. |
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. |
green, orbiculate to ovate, 2.1–6.5 × 1.1–3 mm, width 1/3–7/8 length, not concealing capsule, margins 3-lobed or 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. |
sepals 1–3.5 mm; petals usually yellow, rarely orange, proximally, yellow distally, 2–6(–8) mm, apex rounded; stamens 20–40, 2–4.5 mm, filaments monomorphic, filiform, unlobed; styles 2–3.5(–5) mm. |
Capsules | clavate, 11–31 × 1.5–3 mm, axillary curved to 250° at maturity, usually inconspicuously longitudinally ribbed. |
narrow-cylindric, 7–30 × 1–2.5 mm, axillary curved to 30° at maturity, usually inconspicuously longitudinally ribbed. |
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. |
10–20, in 1 row distal to mid fruit, tan, dark-mottled or not, triangular prisms, surface ± smooth under 10x magnification; recurved flap over hilum absent; seed coat cell outer periclinal wall flat. |
2n | = 36. |
= 18, 36, 72. |
Mentzelia obscura |
Mentzelia dispersa |
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Phenology | Flowering Feb–May. | Flowering (Apr–)May–Aug(–Sep). |
Habitat | Sandy to rocky washes or slopes, desert scrub, Joshua-tree woodlands, roadsides. | Loamy to sandy or rocky slopes, grasslands, scrub, dry forests, roadsides. |
Elevation | 200–1700 m. (700–5600 ft.) | 400–3100 m. (1300–10200 ft.) |
Distribution |
AZ; CA; NV; UT; Mexico (Baja California, Sonora)
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AZ; CA; CO; ID; MT; ND; NV; OR; SD; UT; WA; WY; BC
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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.) |
Mentzelia dispersa is the only polyploid species solely derived from the “Affines” clade and may be an autopolyploid complex (J. M. Brokaw and L. Hufford 2010, 2010b). Morphological characters that consistently distinguish cytotypes within M. dispersa have not been found. Mentzelia dispersa is most easily confused with M. affinis (see discussion under 65. M. affinis) but is phylogenetically distinct (Brokaw and Hufford 2010, 2010b). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 540. | FNA vol. 12, p. 536. |
Parent taxa | Loasaceae > Mentzelia > sect. Trachyphytum | Loasaceae > Mentzelia > sect. Trachyphytum |
Sibling taxa | ||
Synonyms | M. albicaulis var. integrifolia, M. dispersa var. compacta, M. dispersa var. latifolia, M. dispersa var. obtusa, M. pinetorum | |
Name authority | H. J. Thompson & J. E. Roberts: Phytologia 21: 284. (1971) | S. Watson: Proc. Amer. Acad. Arts 11: 137. (1876) |
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