Mentzelia humilis
Mentzelia isolata
gypsum blazingstar
isolated blazingstar
solitary or multiple, erect, straight;
branches distal or along entire stem, distal longest or all ± equal, antrorse; straight to upcurved; hairy.
erect, to 70 cm.
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.
petiole to 25 mm (proximal leaves), absent (distal leaves);
blade usually lanceolate to hastate, rarely elliptic, basally lobed, sometime with 2 pairs of lobes, or unlobed, to 14 × 4.5 cm, base obliquely obtuse to acute, margins shallowly serrate, apex acute.
margins usually entire, rarely pinnate.
(fruiting) 0.5–0.8 × 1–2 mm (often appearing absent because thick and continuous with capsule).
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 orange, 5–7 × 2.3–4 mm, apex cuspidate, hairy on apex and abaxially near apex;
stamens 8–12, 4–5.3 mm, filaments heteromorphic, 5 outermost narrowly spatulate, inner filiform;
styles 3.8–5.5 mm.
cup-shaped, 5.3–10.2 × (4.2–)5.2–8.6 mm, base rounded, not longitudinally ridged.
clavate or funnelform, 12–27 × 3–5 mm, base tapering gradually, capsule and pedicel not well-differentiated.
coat anticlinal cell walls wavy, papillae 6–12 per cell.
8–12 per capsule, pyriform, without transverse folds.
= 20.
Mentzelia humilis
Mentzelia isolata
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 isolata intergrades with both M. aspera and M. asperula in southern Arizona. Typically, M. isolata can be distinguished from both M. aspera and M. asperula because its leaf blades are more than two times as long as wide, whereas those of the latter two species are less than two times as long as wide.
(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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