Mentzelia obscura |
Mentzelia jonesii |
|
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Pacific blazing star |
Jones stickleaf, Jones' blazing star |
|
Habit | Plants candelabra-form, 8–45 cm. | Plants candelabra-form, 20–40(–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 linear-lanceolate to linear, margins deeply lobed to dentate. |
Cauline leaves | petiole absent; blade ovate-lanceolate to linear, to 15(–22) cm, margins few-lobed or entire. |
petiole absent; blade ovate-lanceolate to linear, to 15 cm, margins deeply to shallowly lobed or entire. |
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, ovate to lanceolate, 3.7–5.9 × 0.8–3.9 mm, width 1/8–2/3 length, not concealing capsule, 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. |
sepals (2–)4–8(–10) mm; petals yellow to orange proximally, yellow distally, (6–)8–22 mm, apex acute to rounded; stamens 20+, 3–10 mm, filaments monomorphic, filiform, unlobed; styles 4–10 mm. |
Capsules | clavate, 11–31 × 1.5–3 mm, axillary curved to 250° at maturity, usually inconspicuously longitudinally ribbed. |
clavate, 15–38 × 2–4 mm, axillary curved to 180° or S-shaped 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. |
15–30, in 2+ rows distal to mid fruit, tan, dark-mottled, usually irregularly polygonal, occasionally triangular prisms proximal to mid fruit, surface tuberculate under 10x magnification; recurved flap over hilum absent; seed coat cell outer periclinal wall domed, domes on seed edges more than 1/2 as tall as wide at maturity. |
2n | = 36. |
= 36, 54. |
Mentzelia obscura |
Mentzelia jonesii |
|
Phenology | Flowering Feb–May. | Flowering Mar–May. |
Habitat | Sandy to rocky washes or slopes, desert scrub, Joshua-tree woodlands, roadsides. | Sandy to rocky washes, fans, or flats, creosote-bush scrub, Joshua-tree or saguaro woodlands. |
Elevation | 200–1700 m. (700–5600 ft.) | 200–1500 m. (700–4900 ft.) |
Distribution |
AZ; CA; NV; UT; Mexico (Baja California, Sonora)
|
AZ; CA; NV; 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 jonesii is widespread throughout southeastern California and western and southern Arizona. However, tetraploid populations have been found only in California and far northwestern Arizona. Hexaploids in California have previously been called M. californica. The ranges of M. jonesii and the diploid, M. nitens, overlap in southern Inyo County, California, and these species are difficult to distinguish morphologically without mature seeds; sepal and petal lengths, which have sometimes been used to distinguish them, overlap completely. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 540. | FNA vol. 12, p. 537. |
Parent taxa | Loasaceae > Mentzelia > sect. Trachyphytum | Loasaceae > Mentzelia > sect. Trachyphytum |
Sibling taxa | ||
Synonyms | M. albicaulis var. jonesii, M. californica, M. nitens var. jonesii | |
Name authority | H. J. Thompson & J. E. Roberts: Phytologia 21: 284. (1971) | (Urban & Gilg) H. J. Thompson & J. E. Roberts: Phytologia 21: 282. (1971) |
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