Mentzelia desertorum
Mentzelia tricuspis
desert blazing star
desert blazingstar, spiny-hair blazing star, spinyhair stickleaf, three point blazing star
persisting;
petiole present or absent;
blade linear, margins usually shallowly lobed, lobes rounded.
petioles present;
blade lanceolate, to 12 cm;
margins shallowly lobed, lobes rounded.
petiole absent;
blade ovate-lanceolate to linear, to 12 cm, margins shallowly lobed or entire.
petioles usually present, rarely absent;
blade broadly ovate to lanceolate, to 12 cm, base not cordate-clasping, margins dentate to serrate.
green, ovate to ovate-lanceolate, 3.6–4.7 × 1.6–2.3 mm, width 1/3–1/2 length, not concealing capsule, margins entire.
green, inconspicuous, not concealing pedicel, ovary, or capsule.
sepals 2–4 mm;
petals yellow to orange proximally, yellow distally, 2–6 mm, apex acute or rounded;
stamens 10–30, 2–4 mm, filaments monomorphic, filiform, unlobed;
styles 2–4 mm.
petals white to pale yellow, obovate, 10–30(–50) mm, apex mucronate;
stamens 7–17 mm, less than 1/2 petal length, all fertile, none petaloid (flowers appearing to have 5 petals);
filaments ± monomorphic, linear, distally 2-lobed, lobes 0.6–2.5 mm;
anther stalk usually shorter than filament lobes;
style 10–15 mm.
clavate, 12–27 × 1–2.5 mm, axillary curved to 180° at maturity, usually inconspicuously longitudinally ribbed.
cylindric to ovoid, 9–18(–23) × 5–8 mm, proximal nodding, distal erect.
10–50, 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 tessellate under 10x magnification; recurved flap over hilum absent;
seed coat cell outer periclinal wall flat to slightly convex.
constricted and grooved at middle;
seed coat anticlinal cell walls straight to slightly wavy, conspicuous.
= 18.
= 20.
Mentzelia desertorum
Mentzelia tricuspis
Mentzelia desertorum, a diploid, is most similar morphologically to the tetraploid M. obscura, and the two species may be difficult to distinguish prior to seed maturation. However, many populations of M. desertorum have narrow basal leaves with short, widely spaced lobes that are unique among species within sect. Trachyphytum.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Mentzelia tricuspis is morphologically most similar to M. tridentata with differences largely limited to the lengths of the stamen filament lobes (and thus relative lengths of the anther stalks) and shapes of the seeds. However, the species are also distinct geographically, with M. tricuspis found in the southeastern Mojave Desert and northwestern Sonoran Desert and M. tridentata in the central to western Mojave Desert.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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