Mentzelia obscura |
Mentzelia desertorum |
|
---|---|---|
Pacific blazing star |
desert blazing star |
|
Habit | Plants candelabra-form, 8–45 cm. | Plants candelabra-form, 5–40 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, margins usually shallowly lobed, lobes rounded. |
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 12 cm, margins 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 ovate-lanceolate, 3.6–4.7 × 1.6–2.3 mm, width 1/3–1/2 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 mm; petals yellow to orange proximally, yellow distally, 2–6 mm, apex acute or rounded; stamens 10–30, 2–4 mm, filaments monomorphic, filiform, unlobed; styles 2–4 mm. |
Capsules | clavate, 11–31 × 1.5–3 mm, axillary curved to 250° at maturity, usually inconspicuously longitudinally ribbed. |
clavate, 12–27 × 1–2.5 mm, axillary curved to 180° 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. |
10–50, 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 tessellate under 10x magnification; recurved flap over hilum absent; seed coat cell outer periclinal wall flat to slightly convex. |
2n | = 36. |
= 18. |
Mentzelia obscura |
Mentzelia desertorum |
|
Phenology | Flowering Feb–May. | Flowering Feb–Mar. |
Habitat | Sandy to rocky washes or slopes, desert scrub, Joshua-tree woodlands, roadsides. | Sandy flats, washes, creosote-bush scrub. |
Elevation | 200–1700 m. (700–5600 ft.) | 30–1000 m. (100–3300 ft.) |
Distribution |
AZ; CA; NV; UT; Mexico (Baja California, Sonora)
|
AZ; CA; Mexico (Baja California, 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 desertorum, a diploid, is most similar morphologically to the tetraploid M. obscura, and the two species may be difficult to distinguish prior to seed maturation. However, many populations of M. desertorum have narrow basal leaves with short, widely spaced lobes that are unique among species within sect. Trachyphytum. (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 | Acrolasia desertorum | |
Name authority | H. J. Thompson & J. E. Roberts: Phytologia 21: 284. (1971) | (Davidson) H. J. Thompson & J. E. Roberts: Phytologia 21: 280. (1971) |
Web links |