Mentzelia obscura
Mentzelia albicaulis
Pacific blazing star
small flower blazing star, small-flower evening star, white stem blazing star, white-stem evening star, white-stem stick-leaf
persisting;
petiole present or absent;
blade linear-lanceolate to linear, margins usually irregularly deeply lobed, lobes pointed.
persisting;
petiole present or absent;
blade linear-lanceolate to linear, margins deeply to shallowly lobed.
petiole absent;
blade ovate-lanceolate to linear, to 15(–22) cm, margins few-lobed or entire.
petiole absent;
blade ovate-lanceolate to linear, to 15 cm, margins deeply to shallowly lobed or entire.
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.
green, ovate to linear, 3.7–8.6 × 0.8–3.9 mm, width 1/6–2/3 length, not concealing capsule, margins 3-lobed or entire, lateral lobes never prominent.
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.
sepals 1–5 mm;
petals orange proximally, yellow distally, 3–7(–8) mm, apex usually acute, rarely retuse;
stamens 20+, 3–5 mm, filaments monomorphic, filiform, unlobed;
styles 2–5 mm.
clavate, 11–31 × 1.5–3 mm, axillary curved to 250° at maturity, usually inconspicuously longitudinally ribbed.
clavate, 8–28(–35) × 1.5–3.5 mm, longest capsules usually 15+ mm, axillary curved to 180° at maturity, usually inconspicuously longitudinally ribbed.
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.
10–30, in 2+ rows distal to mid fruit, dark brown or tan, moderately to densely dark-mottled, usually irregularly polygonal, occasionally triangular prisms proximal to mid fruit, surface tuberculate under 10x magnification; recurved flap over hilum absent;
seed coat cell outer periclinal wall domed, domes on seed edges more than 1/2 as tall as wide at maturity.
= 36.
= 54, 72.
Mentzelia obscura
Mentzelia albicaulis
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.)
Mentzelia albicaulis is the most widespread species in sect. Trachyphytum and exhibits extensive morphological variation. Most populations of M. albicaulis are octoploid; however, hexaploids from southern California that have been called M. mojavensis and occasionally M. californica are also treated here as M. albicaulis. Two tetraploids in sect. Trachyphytum, M. montana and M. obscura, also have been treated previously as M. albicaulis (N. H. Holmgren et al. 2005). Both exhibit morphological forms and distributions overlapping with M. albicaulis. However, in most cases these species can be distinguished without chromosome counts, and their distinctiveness has been supported by phylogenetic analyses (J. M. Brokaw and L. Hufford 2010b).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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