Mentzelia humilis
Mentzelia nuda
gypsum blazingstar
bractless blazingstar, goodmother, naked blazingstar or western star, stickleaf mentzelia
solitary or multiple, erect, straight;
branches distal or along entire stem, distal longest or all ± equal, antrorse; straight to upcurved; hairy.
solitary (or multiple as wound response), erect, straight;
branches distal, distal longest, antrorse, straight; hairy.
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.
blade 37–120 × 5–24.4 mm, widest intersinus distance 4.8–19.6 mm;
proximal oblanceolate to elliptic, margins serrate, teeth 14–30, slightly antrorse, 0.6–4.9 mm;
distal elliptic to lanceolate, base not clasping, margins serrate, teeth 12–30, slightly antrorse, 0.7–4.7 mm;
abaxial surface with simple grappling-hook, complex grappling-hook, and needlelike trichomes, adaxial surface with simple grappling-hook and needlelike trichomes.
margins usually entire, rarely pinnate.
margins pinnate.
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.
petals white, 22.6–49 × 3.6–10.3 mm, apex acute, glabrous abaxially, stamens white, 5 outermost petaloid, filaments narrowly spatulate, slightly clawed, 20–47 × 3–10.2 mm, without anthers, second whorl without anthers;
anthers straight after dehiscence, epidermis smooth;
styles 11.5–18.5 mm.
cup-shaped, 5.3–10.2 × (4.2–)5.2–8.6 mm, base rounded, not longitudinally ridged.
cylindric, 14.5–29 × 6.9–12.3 mm, base tapering or rounded, not longitudinally ridged.
coat anticlinal cell walls wavy, papillae 6–12 per cell.
coat anticlinal cell walls wavy, papillae 4–8 per cell.
= 20.
Mentzelia humilis
Mentzelia nuda
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.)
Mentzelia nuda is morphologically similar to, and phylogenetically near, M. strictissima (J. J. Schenk 2009), but it can be distinguished from the latter by its much larger flowers and capsules. The two species have adjacent ranges in New Mexico and Texas but do not overlap despite apparently similar habitat requirements. Mentzelia strictissima occurs west and south of M. nuda and abuts against the southernmost portion of the Rocky Mountains. In the northern portion of its range, M. nuda too approaches the foothills of the southern Rocky Mountains and extends eastward into the plains. Mentzelia nuda was collected once in northeastern Illinois in 1901 but apparently did not become established there. Reports of M. nuda from Arizona are based on misidentified material of M. laevicaulis and M. rusbyi.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaf blade widest intersinus distances 0.8–2.6(–3.3) mm; lobes of proximal leaves 1–2.9 mm wide. | var. humilis |
1. Leaf blade widest intersinus distances 1.6–9.1 mm (always on some leaves greater than 2.6 mm); lobes of proximal leaves (1.1–)2.9–5.1 mm wide. | var. guadalupensis |
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