Mentzelia albescens |
Mentzelia desertorum |
|
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wavy-leaf blazingstar |
desert blazing star |
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Habit | Plants biennial, candelabra-form. | Plants candelabra-form, 5–40 cm. |
Stems | solitary, erect, straight; branches distal, distal longest, antrorse, straight; hairy. |
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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. |
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Basal leaves | persisting; petiole present or absent; blade linear, margins usually shallowly lobed, lobes rounded. |
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Cauline leaves | petiole absent; blade ovate-lanceolate to linear, to 12 cm, margins shallowly lobed or entire. |
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Bracts | 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 | 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. |
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 | cylindric, 13.6–23.5 × 5.1–7.8 mm, base tapering, not or slightly longitudinally ridged. |
clavate, 12–27 × 1–2.5 mm, axillary curved to 180° at maturity, usually inconspicuously longitudinally ribbed. |
Seeds | coat anticlinal cell walls straight, papillae 4–17 per cell. |
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 | = 22. |
= 18. |
Mentzelia albescens |
Mentzelia desertorum |
|
Phenology | Flowering May–Nov. | Flowering Feb–Mar. |
Habitat | Dry grasslands, xeric habitats of arroyos, roadsides, roadcuts, washes, chat piles, slopes. | Sandy flats, washes, creosote-bush scrub. |
Elevation | 200–1600 m. (700–5200 ft.) | 30–1000 m. (100–3300 ft.) |
Distribution |
KS; MO; OK; TX; South America (Argentina, Chile) |
AZ; CA; Mexico (Baja California, Sonora) |
Discussion | 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.) |
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. 518. | FNA vol. 12, p. 536. |
Parent taxa | Loasaceae > Mentzelia > sect. Bartonia | Loasaceae > Mentzelia > sect. Trachyphytum |
Sibling taxa | ||
Synonyms | Bartonia albescens, B. wrightii | Acrolasia desertorum |
Name authority | (Gillies ex Arnott) Bentham & Hooker f. ex Grisebach: Abh. Königl. Ges. Wiss. Göttingen 19: 150. (1874) | (Davidson) H. J. Thompson & J. E. Roberts: Phytologia 21: 280. (1971) |
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