Mentzelia humilis
Mentzelia leucophylla
gypsum blazingstar
Ash Meadows blazingstar
solitary or multiple, erect, straight;
branches distal or along entire stem, distal longest or all ± equal, antrorse; straight to upcurved; hairy.
multiple, erect, straight;
branches distal or along entire stem, distal longest or all ± equal, 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 15–61 × 8–28.5 mm, widest intersinus distance 6–23.8 mm;
proximal obovate, ovate, or broadly elliptic, margins usually dentate to serrate, rarely entire, teeth (0–)6–20, slightly antrorse or perpendicular to leaf axis, 0.4–4 mm;
distal deltate to cordate, base clasping, margins usually dentate, rarely entire, teeth (0–)6–12, perpendicular to leaf axis, 0.5–2 mm;
abaxial surface with complex grappling-hook and needlelike trichomes, adaxial surface with needlelike trichomes, both surfaces whitish, densely hairy.
margins usually entire, rarely pinnate.
margins entire.
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 golden yellow, 9.2–13.2 × 2.8–5 mm, apex rounded, glabrous abaxially;
stamens golden yellow, 5 outermost petaloid, filaments narrowly spatulate, slightly clawed, 6–10.6 × 1.3–2.6 mm, with anthers, second whorl with anthers;
anthers twisted or straight after dehiscence, epidermis smooth;
styles 6–8.1 mm.
cup-shaped, 5.3–10.2 × (4.2–)5.2–8.6 mm, base rounded, not longitudinally ridged.
cup-shaped, 5–9.5 × 6–8.6 mm, base rounded, not longitudinally ridged.
coat anticlinal cell walls wavy, papillae 6–12 per cell.
coat anticlinal cell walls straight, papillae 11–13 per cell.
= 36.
Mentzelia humilis
Mentzelia leucophylla
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 leucophylla is known only from the Ash Meadows of Nye County (N. H. Holmgren et al. 2005). It is morphologically similar to M. oreophila, which occurs in Nye County and elsewhere, but the two taxa are not known to co-occur. Trichome density, despite being difficult to quantify, provides perhaps the easiest method to differentiate the two taxa, with the densely hairy leaves of M. leucophylla appearing whitish. In addition to characters provided in the key, M. leucophylla, which is up to seven decimeters tall, is often more robust than M. oreophila, which is no more than six decimeters tall.
(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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