Mentzelia obscura |
Mentzelia albescens |
|
---|---|---|
Pacific blazing star |
wavy-leaf blazingstar |
|
Habit | Plants candelabra-form, 8–45 cm. | Plants biennial, candelabra-form. |
Stems | solitary, erect, straight; branches distal, distal longest, antrorse, straight; hairy. |
|
Leaves | blade 31–92(–157) × 10.5–27.6(–41) mm, widest intersinus distance 5.2–23.3(–29) mm; proximal lanceolate or elliptic, margins serrate to pinnate, teeth or lobes 8–22, slightly antrorse, 1.8–6 mm; distal lanceolate, base clasping, margins usually serrate to pinnate, occasionally entire, teeth or lobes (0–)10–20, slightly antrorse, 1.4–7.6 mm; abaxial surface with simple grappling-hook, complex grappling-hook, and needlelike trichomes, adaxial surface with simple grappling-hook and needlelike trichomes. |
|
Basal leaves | persisting; petiole present or absent; blade linear-lanceolate to linear, margins usually irregularly deeply lobed, lobes pointed. |
|
Cauline leaves | petiole absent; blade ovate-lanceolate to linear, to 15(–22) cm, margins few-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. |
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. |
petals golden yellow, 5.7–9.2 × 1.3–3 mm, apex usually acute, occasionally rounded, glabrous abaxially; stamens golden yellow, 5 outermost petaloid, filaments narrowly spatulate, slightly clawed, 4.7–8.4 × 1–2.4 mm, without anthers, second whorl with anthers; anthers straight after dehiscence, epidermis smooth; styles 3.5–5.4 mm. |
Capsules | clavate, 11–31 × 1.5–3 mm, axillary curved to 250° at maturity, usually inconspicuously longitudinally ribbed. |
cylindric, 13.6–23.5 × 5.1–7.8 mm, base tapering, not or slightly 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 4–17 per cell. |
2n | = 36. |
= 22. |
Mentzelia obscura |
Mentzelia albescens |
|
Phenology | Flowering Feb–May. | Flowering May–Nov. |
Habitat | Sandy to rocky washes or slopes, desert scrub, Joshua-tree woodlands, roadsides. | Dry grasslands, xeric habitats of arroyos, roadsides, roadcuts, washes, chat piles, slopes. |
Elevation | 200–1700 m. (700–5600 ft.) | 200–1600 m. (700–5200 ft.) |
Distribution |
AZ; CA; NV; UT; Mexico (Baja California, Sonora)
|
KS; MO; OK; TX; South America (Argentina, Chile) |
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.) |
Phylogenetic analyses (J. J. Schenk and L. Hufford 2011) recovered representative populations of Mentzelia albescens from Texas and South America in a monophyletic group. Phylogenetic placement of these populations among lineages in sect. Bartonia, as well as a lack of morphological differentiation among North American and South American populations, suggests a recent dispersal to South America. In the flora area, this species is native to central and western Texas, and introduced in Kansas, Missouri, and Oklahoma. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 540. | FNA vol. 12, p. 518. |
Parent taxa | Loasaceae > Mentzelia > sect. Trachyphytum | Loasaceae > Mentzelia > sect. Bartonia |
Sibling taxa | ||
Synonyms | Bartonia albescens, B. wrightii | |
Name authority | H. J. Thompson & J. E. Roberts: Phytologia 21: 284. (1971) | (Gillies ex Arnott) Bentham & Hooker f. ex Grisebach: Abh. Königl. Ges. Wiss. Göttingen 19: 150. (1874) |
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