Mentzelia humilis

(Urban & Gilg) J. Darlington

Ann. Missouri Bot. Gard. 21: 155. 1934.

Basionym: Mentzelia pumila var. humilis Urban & Gilg Nova Acta Acad. Caes. Leop.-Carol. German. Nat. Cur. 76: 93. 1900
Synonyms: Nuttallia humilis (Urban & Gilg) Rydberg Touterea humilis (Urban & Gilg) Rydberg
Treatment appears in FNA Volume 12. Treatment on page 503. Mentioned on page 499, 542, 543.

Plants perennial, bushlike, with ground-level caudices. Stems solitary or multiple, erect, straight; branches distal or along entire stem, distal longest or all ± equal, antrorse; straight to upcurved; hairy. Leaves: 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. Bracts: margins usually entire, rarely pinnate. Flowers: 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. Capsules cup-shaped, 5.3–10.2 × (4.2–)5.2–8.6 mm, base rounded, not longitudinally ridged. Seeds: coat anticlinal cell walls wavy, papillae 6–12 per cell.


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, 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.

Selected References



1 Leaf blade widest intersinus distances 0.8–2.6(–3.3) mm; lobes of proximal leaves 1–2.9 mm wide. Mentzelia humilis 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. Mentzelia humilis var. guadalupensis