Mentzelia albicaulis
Mentzelia desertorum
small flower blazing star, small-flower evening star, white stem blazing star, white-stem evening star, white-stem stick-leaf
desert blazing star
persisting;
petiole present or absent;
blade linear-lanceolate to linear, margins deeply to shallowly lobed.
persisting;
petiole present or absent;
blade linear, margins usually shallowly lobed, lobes rounded.
petiole absent;
blade ovate-lanceolate to linear, to 15 cm, margins deeply to shallowly lobed or entire.
petiole absent;
blade ovate-lanceolate to linear, to 12 cm, margins shallowly lobed or 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.
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.
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.
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.
clavate, 8–28(–35) × 1.5–3.5 mm, longest capsules usually 15+ mm, axillary curved to 180° at maturity, usually inconspicuously longitudinally ribbed.
clavate, 12–27 × 1–2.5 mm, axillary curved to 180° at maturity, usually inconspicuously longitudinally ribbed.
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.
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.
= 54, 72.
= 18.
Mentzelia albicaulis
Mentzelia desertorum
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.)
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.)
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