Mentzelia humilis
Mentzelia obscura
gypsum blazingstar
Pacific blazing star
solitary or multiple, erect, straight;
branches distal or along entire stem, distal longest or all ± equal, antrorse; straight to upcurved; 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.
persisting;
petiole present or absent;
blade linear-lanceolate to linear, margins usually irregularly deeply lobed, lobes pointed.
petiole absent;
blade ovate-lanceolate to linear, to 15(–22) cm, margins few-lobed or entire.
margins usually entire, rarely pinnate.
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.
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.
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.
cup-shaped, 5.3–10.2 × (4.2–)5.2–8.6 mm, base rounded, not longitudinally ridged.
clavate, 11–31 × 1.5–3 mm, axillary curved to 250° at maturity, usually inconspicuously longitudinally ribbed.
coat anticlinal cell walls wavy, papillae 6–12 per cell.
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.
= 36.
Mentzelia humilis
Mentzelia obscura
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 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.)
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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