Mentzelia obscura |
Mentzelia hirsutissima |
|
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Pacific blazing star |
hairy blazingstar, hairy stickleaf |
|
Habit | Plants candelabra-form, 8–45 cm. | Plants (5–)15–30(–40) cm. |
Basal leaves | persisting; petiole present or absent; blade linear-lanceolate to linear, margins usually irregularly deeply lobed, lobes pointed. |
petioles present or absent; blade oblanceolate, to 11 cm; margins shallowly lobed, lobes rounded. |
Cauline leaves | petiole absent; blade ovate-lanceolate to linear, to 15(–22) cm, margins few-lobed or entire. |
petioles absent; blade ovate to lanceolate, to 11 cm, base often cordate-clasping, margins deeply to shallowly lobed, lobes acute. |
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, inconspicuous, not concealing pedicel, ovary, or capsule. |
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, obovate, 12–31 mm, apex mucronate; stamens 4–12 mm, less than 1/2 petal length, all fertile, none petaloid (flowers appearing to have 5 petals); filaments ±monomorphic, linear, most or all distally 2-lobed, lobes to 0.3 mm; anther stalk longer than filament lobes; style 6–15 mm. |
Capsules | clavate, 11–31 × 1.5–3 mm, axillary curved to 250° at maturity, usually inconspicuously longitudinally ribbed. |
cylindric to cup-shaped, 13–25 × 5–8 mm, erect. |
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. |
widest at middle, not grooved; seed coat anticlinal cell walls deeply wavy. |
2n | = 36. |
|
Mentzelia obscura |
Mentzelia hirsutissima |
|
Phenology | Flowering Feb–May. | Flowering Apr–May. |
Habitat | Sandy to rocky washes or slopes, desert scrub, Joshua-tree woodlands, roadsides. | Washes, fans, slopes, desert scrub. |
Elevation | 200–1700 m. (700–5600 ft.) | 0–800 m. (0–2600 ft.) |
Distribution |
AZ; CA; NV; UT; Mexico (Baja California, Sonora)
|
CA; Mexico (Baja California, Baja California Sur, Sonora) |
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 hirsutissima is superficially similar to M. tricuspis and M. tridentata, but these taxa can be distinguished geographically. Mentzelia hirsutissima is distributed primarily on the Baja California Peninsula and occurs in California only in San Diego and far western Imperial counties, whereas M. tricuspis and M. tridentata occur north and east of this distribution. California populations previously have been called M. hirsutissima var. stenophylla. However, G. S. Daniels (1970) found that characters used to distinguish varieties of M. hirsutissima were not stable within populations. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 540. | FNA vol. 12, p. 525. |
Parent taxa | Loasaceae > Mentzelia > sect. Trachyphytum | Loasaceae > Mentzelia > sect. Bicuspidaria |
Sibling taxa | ||
Synonyms | M. hirsutissima var. stenophylla, M. stenophylla | |
Name authority | H. J. Thompson & J. E. Roberts: Phytologia 21: 284. (1971) | S. Watson: Proc. Amer. Acad. Arts 12: 252. (1877) |
Web links |