Mentzelia albicaulis |
Mentzelia humilis |
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small flower blazing star, small-flower evening star, white stem blazing star, white-stem evening star, white-stem stick-leaf |
gypsum blazingstar |
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Habit | Plants wandlike or candelabra-form, (2–)10–40(–50) cm. | Plants perennial, bushlike, with ground-level caudices. | ||||
Stems | solitary or multiple, erect, straight; branches distal or along entire stem, distal longest or all ± equal, antrorse; straight to upcurved; hairy. |
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Leaves | blade 25–95 × 5.5–28(–36.2) mm, widest intersinus distance 0.8–9.1 mm; proximal spatulate to oblanceolate or elliptic, margins pinnate to pinnatisect, lobes 4–16(–20), slightly antrorse or perpendicular to leaf axis, 2.3–11.8(–16.4) mm; distal elliptic, lanceolate, spatulate, or linear, base not clasping, margins entire or dentate to pinnatisect, teeth or lobes (0–)4–16, slightly antrorse or perpendicular to leaf axis, 2.3–13.8(–16.9) mm; abaxial surface with simple grappling-hook, needlelike, and sometimes complex grappling-hook trichomes, adaxial surface with simple grappling-hook and needlelike trichomes. |
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Basal leaves | persisting; petiole present or absent; blade linear-lanceolate to linear, margins deeply to shallowly lobed. |
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Cauline leaves | petiole absent; blade ovate-lanceolate to linear, to 15 cm, margins deeply to shallowly lobed or entire. |
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Bracts | green, ovate to linear, 3.7–8.6 × 0.8–3.9 mm, width 1/6–2/3 length, not concealing capsule, margins 3-lobed or entire, lateral lobes never prominent. |
margins usually entire, rarely pinnate. |
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Flowers | sepals 1–5 mm; petals orange proximally, yellow distally, 3–7(–8) mm, apex usually acute, rarely retuse; stamens 20+, 3–5 mm, filaments monomorphic, filiform, unlobed; styles 2–5 mm. |
petals white, 10.3–13(–28.6) × 1.4–4 mm, apex acute, glabrous abaxially; stamens white, 5 outermost petaloid, filaments linear to narrowly spatulate, slightly clawed, 8.8–19(–22.3) × 0.7–3.3 mm, without anthers, second whorl without anthers; anthers straight after dehiscence, epidermis papillate; styles 6.5–11.3 mm. |
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Capsules | clavate, 8–28(–35) × 1.5–3.5 mm, longest capsules usually 15+ mm, axillary curved to 180° at maturity, usually inconspicuously longitudinally ribbed. |
cup-shaped, 5.3–10.2 × (4.2–)5.2–8.6 mm, base rounded, not longitudinally ridged. |
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Seeds | 10–30, in 2+ rows distal to mid fruit, dark brown or tan, moderately to densely 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. |
coat anticlinal cell walls wavy, papillae 6–12 per cell. |
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2n | = 54, 72. |
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Mentzelia albicaulis |
Mentzelia humilis |
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Phenology | Flowering Mar–Aug. | |||||
Habitat | Sand dunes, gravel fans, washes, desert scrub, sagebrush or antelope bitterbrush scrub, open ponderosa pine woodlands, pinyon/juniper woodlands. | |||||
Elevation | 0–2300 m. (0–7500 ft.) | |||||
Distribution |
AZ; CA; CO; ID; MT; NE; NM; NV; OR; SD; TX; UT; WA; WY; BC; SK; Mexico (Baja California, Chihuahua, Sonora)
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NM; TX
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Discussion | Mentzelia albicaulis is the most widespread species in sect. Trachyphytum and exhibits extensive morphological variation. Most populations of M. albicaulis are octoploid; however, hexaploids from southern California that have been called M. mojavensis and occasionally M. californica are also treated here as M. albicaulis. Two tetraploids in sect. Trachyphytum, M. montana and M. obscura, also have been treated previously as M. albicaulis (N. H. Holmgren et al. 2005). Both exhibit morphological forms and distributions overlapping with M. albicaulis. However, in most cases these species can be distinguished without chromosome counts, and their distinctiveness has been supported by phylogenetic analyses (J. M. Brokaw and L. Hufford 2010b). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Varieties 2 (2 in the flora). The basionym of Mentzelia humilis is often cited as M. multiflora var. humilis A. Gray (1852). However, in that publication Gray indicated accepted names in Roman capitals (see ipni.org), whereas the varietal name is in lower case, indicating that he was using it as a descriptive term rather than a scientific name. Valid publication of the basionym thus must be attributed to Urban and Gilg. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 12, p. 534. | FNA vol. 12, p. 503. | ||||
Parent taxa | Loasaceae > Mentzelia > sect. Trachyphytum | Loasaceae > Mentzelia > sect. Bartonia | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Bartonia albicaulis, M. mojavensis | M. pumila var. humilis, Nuttallia humilis, Touterea humilis | ||||
Name authority | (Douglas) Douglas ex Torrey & A. Gray: Fl. N. Amer. 1: 534. (1840) | (Urban & Gilg) J. Darlington: Ann. Missouri Bot. Gard. 21: 155. (1934) | ||||
Web links |