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Pacific blazing star

sand blazing star, white-bract blazing star

Habit Plants candelabra-form, 8–45 cm. Plants 7–35(–45) 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 lanceolate, to 10(–16) cm;

margins shallowly to deeply lobed, lobes acute.

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 10(–16) 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.

white with green margins, conspicuous, concealing pedicel, ovary, and 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 white to pale yellow, usually with orange veins, obovate, 13–65 mm, apex mucronate;

stamens 4–26 mm, less than 1/2 petal length, all fertile, none petaloid (flowers appearing to have 5 petals);

filaments ± monomorphic, linear, distally 2-lobed, lobes 0.5–2 mm;

anther stalk shorter or longer than filament lobes;

style 8–30 mm.

Capsules

clavate, 11–31 × 1.5–3 mm, axillary curved to 250° at maturity, usually inconspicuously longitudinally ribbed.

cylindric to cup-shaped, 14–25(–30) × 5–10 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.

usually constricted proximal to middle;

seed coat anticlinal cell walls wavy.

2n

= 36.

= 18.

Mentzelia obscura

Mentzelia involucrata

Phenology Flowering Feb–May. Flowering Jan–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.) 50–900 m. (200–3000 ft.)
Distribution
from FNA
AZ; CA; NV; UT; Mexico (Baja California, Sonora)
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[BONAP county map]
from FNA
AZ; CA; Mexico (Baja California, Sonora)
[WildflowerSearch map]
[BONAP county map]
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 involucrata is easily distinguished from other species in sect. Bicuspidaria by its large white bracts, which are strikingly similar to those of M. congesta in sect. Trachyphytum. Phylogenetic studies show that these species are not closely related, suggesting a homoplasious origin of the characteristic (J. M. Brokaw and L. Hufford, 2010). Populations exhibiting petals longer than 3 cm have previously been called var. megalantha. However, a study by G. S. Daniels (1970) suggested that insufficient geographic and morphological discontinuities exist for recognition of varieties.

P. A. Munz (1974) mistakenly cited var. megalantha as Mentzelia involucrata subsp. megalantha I. M. Johnston, a name never validly published.

(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
M. affinis, M. albescens, M. albicaulis, M. argillicola, M. argillosa, M. aspera, M. asperula, M. candelariae, M. canyonensis, M. chrysantha, M. collomiae, M. congesta, M. conspicua, M. crocea, M. cronquistii, M. decapetala, M. densa, M. desertorum, M. dispersa, M. eremophila, M. filifolia, M. floridana, M. flumensevera, M. goodrichii, M. gracilenta, M. hirsutissima, M. holmgreniorum, M. hualapaiensis, M. humilis, M. integra, M. involucrata, M. inyoensis, M. isolata, M. jonesii, M. laciniata, M. laevicaulis, M. lagarosa, M. leucophylla, M. librina, M. lindheimeri, M. lindleyi, M. longiloba, M. marginata, M. memorabilis, M. mexicana, M. micrantha, M. mollis, M. monoensis, M. montana, M. multicaulis, M. multiflora, M. nitens, M. nuda, M. oligosperma, M. oreophila, M. pachyrhiza, M. packardiae, M. paradoxensis, M. pectinata, M. perennis, M. polita, M. procera, M. pterosperma, M. puberula, M. pumila, M. ravenii, M. reflexa, M. reverchonii, M. rhizomata, M. rusbyi, M. saxicola, M. shultziorum, M. sivinskii, M. speciosa, M. springeri, M. strictissima, M. thompsonii, M. tiehmii, M. todiltoensis, M. torreyi, M. tricuspis, M. tridentata, M. uintahensis, M. veatchiana
M. affinis, M. albescens, M. albicaulis, M. argillicola, M. argillosa, M. aspera, M. asperula, M. candelariae, M. canyonensis, M. chrysantha, M. collomiae, M. congesta, M. conspicua, M. crocea, M. cronquistii, M. decapetala, M. densa, M. desertorum, M. dispersa, M. eremophila, M. filifolia, M. floridana, M. flumensevera, M. goodrichii, M. gracilenta, M. hirsutissima, M. holmgreniorum, M. hualapaiensis, M. humilis, M. integra, M. inyoensis, M. isolata, M. jonesii, M. laciniata, M. laevicaulis, M. lagarosa, M. leucophylla, M. librina, M. lindheimeri, M. lindleyi, M. longiloba, M. marginata, M. memorabilis, M. mexicana, M. micrantha, M. mollis, M. monoensis, M. montana, M. multicaulis, M. multiflora, M. nitens, M. nuda, M. obscura, M. oligosperma, M. oreophila, M. pachyrhiza, M. packardiae, M. paradoxensis, M. pectinata, M. perennis, M. polita, M. procera, M. pterosperma, M. puberula, M. pumila, M. ravenii, M. reflexa, M. reverchonii, M. rhizomata, M. rusbyi, M. saxicola, M. shultziorum, M. sivinskii, M. speciosa, M. springeri, M. strictissima, M. thompsonii, M. tiehmii, M. todiltoensis, M. torreyi, M. tricuspis, M. tridentata, M. uintahensis, M. veatchiana
Synonyms M. involucrata var. megalantha
Name authority H. J. Thompson & J. E. Roberts: Phytologia 21: 284. (1971) S. Watson: Proc. Amer. Acad. Arts 20: 367. (1885)
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