Mentzelia pectinata
Mentzelia leucophylla
San Joaquin blazing star
Ash Meadows blazingstar
multiple, erect, straight;
branches distal or along entire stem, distal longest or all ± equal, antrorse, straight; hairy.
blade 15–61 × 8–28.5 mm, widest intersinus distance 6–23.8 mm;
proximal obovate, ovate, or broadly elliptic, margins usually dentate to serrate, rarely entire, teeth (0–)6–20, slightly antrorse or perpendicular to leaf axis, 0.4–4 mm;
distal deltate to cordate, base clasping, margins usually dentate, rarely entire, teeth (0–)6–12, perpendicular to leaf axis, 0.5–2 mm;
abaxial surface with complex grappling-hook and needlelike trichomes, adaxial surface with needlelike trichomes, both surfaces whitish, densely hairy.
persisting;
petiole present or absent;
blade lanceolate to linear, margins deeply to shallowly lobed.
petiole absent;
blade ovate to linear, to 12 cm, margins deeply lobed to dentate.
green, ovate to lanceolate, 6.6–12.8 × 1.9–6.8 mm, width 1/5–2/3 length, not concealing capsule, margins 3–7-lobed.
margins entire.
sepals 3–13 mm;
petals red to orange proximally, orange to yellow distally, 8–22 mm, apex mucronate, rounded, or retuse;
stamens 20+, 4–11 mm, filaments monomorphic, filiform, unlobed;
styles 5–13 mm.
petals golden yellow, 9.2–13.2 × 2.8–5 mm, apex rounded, glabrous abaxially;
stamens golden yellow, 5 outermost petaloid, filaments narrowly spatulate, slightly clawed, 6–10.6 × 1.3–2.6 mm, with anthers, second whorl with anthers;
anthers twisted or straight after dehiscence, epidermis smooth;
styles 6–8.1 mm.
clavate, 12–35 × 2–4 mm, axillary curved to 90° at maturity, usually inconspicuously longitudinally ribbed.
cup-shaped, 5–9.5 × 6–8.6 mm, base rounded, not longitudinally ridged.
20–40, in 2+ rows distal to mid fruit, tan, dark-mottled or not, 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.
coat anticlinal cell walls straight, papillae 11–13 per cell.
= 18.
= 36.
Mentzelia pectinata
Mentzelia leucophylla
Mentzelia pectinata occurs in Kern, San Luis Obispo, Santa Barbara, and Tulare counties, around the southern rim of the San Joaquin Valley, extending into the Inner Coast Ranges and the southern foothills of the Sierra Nevada. Petal color varies from orange to yellow, and fully fertile artificial hybrids have been obtained between populations representing the extreme phenotypes (J. E. Zavortink 1966). Phylogenetic studies suggest that M. pectinata and M. congesta have hybridized to form several allopolyploid species (J. M. Brokaw and L. Hufford 2010b) despite their current allopatric distributions.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Mentzelia leucophylla is known only from the Ash Meadows of Nye County (N. H. Holmgren et al. 2005). It is morphologically similar to M. oreophila, which occurs in Nye County and elsewhere, but the two taxa are not known to co-occur. Trichome density, despite being difficult to quantify, provides perhaps the easiest method to differentiate the two taxa, with the densely hairy leaves of M. leucophylla appearing whitish. In addition to characters provided in the key, M. leucophylla, which is up to seven decimeters tall, is often more robust than M. oreophila, which is no more than six decimeters tall.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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