Mentzelia obscura
Mentzelia lindheimeri
Pacific blazing star
Lindheimer's blazingstar, Lindheimer's stickleaf, Texas stickleaf
erect to decumbent or clambering, to 50 cm.
petiole to 35 mm;
blade usually hastate to ovate, sometimes smallest distal elliptic, basally lobed or unlobed, to 12 × 7.5 cm, base truncate to obtusely cuneate, margins serrate, dentate, or crenulate, apex acute.
persisting;
petiole present or absent;
blade linear-lanceolate to linear, margins usually irregularly deeply lobed, lobes pointed.
petiole absent;
blade ovate-lanceolate to linear, to 15(–22) cm, margins few-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.
(fruiting) 1–5 × less than 1 mm.
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.
petals yellow to orange, 6.5–17 × 4–9.5 mm, apex cuspidate, hairy on apex and abaxially near apex;
stamens (10–)20–45, 5–12(–20) mm, filaments monomorphic, filiform;
style 3.5–13 mm.
clavate, 11–31 × 1.5–3 mm, axillary curved to 250° at maturity, usually inconspicuously longitudinally ribbed.
usually clavate to funnelform, sometimes slightly ovoid, 8–18 × 3.3–4.5 mm, base rounded or cuneate, capsule and pedicel well-differentiated.
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.
(4–)5–10 per capsule, pyriform, without transverse folds.
= 36.
= 20.
Mentzelia obscura
Mentzelia lindheimeri
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.)
As with most species of sect. Mentzelia first described by Urban and Gilg, the delimitation of M. lindheimeri has not been well understood. Phylogenetic results indicate that populations consistent with the types of M. lindheimeri and M. texana are part of a clade restricted to Gulf coastal areas from Florida to northeastern Mexico that also includes M. floridana and M. gracilis. Populations consistent with the M. lindheimeri and M. texana types overlap, and we treat M. texana as a synonym of the former. Mentzelia lindheimeri as treated here is restricted mostly to subtropical southeastern Texas. It is rare in trans-Pecos Texas, although we identified populations of M. lindheimeri in the Davis Mountains. Texas collections annotated as M. incisa Urban & Gilg by Thompson and Zavortink, which served as the basis for Texas reports of that species (for example, D. S. Correll and M. C. Johnston 1970; B. L. Turner et al. 2003) are treated here as M. lindheimeri.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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