Mentzelia pachyrhiza

I. M. Johnston

J. Arnold Arbor. 21: 71. 1940.

Common names: Big-rooted stickleaf
Treatment appears in FNA Volume 12. Treatment on page 529. Mentioned on page 527, 530.

Plants perennial, with tubers. Stems erect, to 50 cm. Leaves: petiole mostly 3–20 mm, less than 3 mm only on smallest, distalmost leaves; blade ovate to hastate, basally lobed or unlobed, to 4 × 3 cm, base usually acute to obtuse, sometimes attenuate or hastate, margins usually serrate, sometimes crenate, apex acute. Pedicels (fruiting) (0–) 2 × 2 mm. Flowers: petals orange, 5–11.5 × 3–5 mm, apex acute to rounded, hairy abaxially on distal 1/2; stamens 15–45, 4–8 mm, filaments usually monomorphic, filiform, rarely heteromorphic, outermost slightly spatulate, inner filiform; style 3–7.5 mm. Capsules subcylindric to clavate, 6–10 × 1.5–2.3 mm, base tapering gradually, capsule and pedicel not well-differentiated, walls thin, brittle. Seeds 2–3 per capsule, oblong, with transverse folds. 2n = 22.


Phenology: Flowering May–Nov.
Habitat: Steep limestone cliffs, gravelly slopes of gypseous clayey soils, desert scrub and Larrea communities.
Elevation: 900–2000 m.

Distribution

V12 568-distribution-map.jpg

Tex., Mexico (Chihuahua), Mexico (Coahuila), Mexico (Durango), Mexico (Nuevo León)

Discussion

Mentzelia pachyrhiza, native to the Chihuahuan Desert, reaches the flora area only in southern Brewster and Presidio counties. In southwestern Texas and northeastern Chihuahua, where M. pachyrhiza and M. oligosperma have overlapping ranges, H. J. Thompson and A. M. Powell (1981) reported that the former was found at elevations usually below 1100 meters in the Larrea zone, below the elevation of junipers and M. oligosperma. Thompson and Powell allied M. pachyrhiza with M. oligosperma and the South American M. grisebachii Urban & Gilg, now treated as a synonym of M. parvifolia Urban & Gilg ex Kurtz (M. Weigend 2007b). This placement is consistent with phylogenetic studies (J. Grissom and L. Hufford, unpubl.), which show that M. pachyrhiza is the sister species of M. parvifolia; they together are the sister of M. oligosperma and the Mexican M. pattersonii B. L. Turner. I. M. Johnston’s (1940) assertion that the large tuber of M. pachyrhiza is unique in sect. Mentzelia is incorrect. Tubers, often carrot-shaped, are common among the perennial species of the section.

Selected References

None.

Lower Taxa

None.
... more about "Mentzelia pachyrhiza"
heteromorphic +  and monomorphic +
inner +  and outer +
filiform +
acute +  and rounded +
Larry Hufford +
I. M. Johnston +
tapering +, hastate +, attenuate +, usually acute +  and obtuse +
0 cm0 mm <br />0 m <br /> (4 cm40 mm <br />0.04 m <br />) +
ovate;hastate basally lobed or unlobed +
0 cm0 mm <br />0 m <br /> (3 cm30 mm <br />0.03 m <br />) +
curved +  and straight +
0.6 cm6 mm <br />0.006 m <br /> (1 cm10 mm <br />0.01 m <br />) +
subcylindric +  and clavate +
not well-differentiated +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.23 cm2.3 mm <br />0.0023 m <br />) +
Big-rooted stickleaf +
Tex. +, Mexico (Chihuahua) +, Mexico (Coahuila) +, Mexico (Durango) +  and Mexico (Nuevo León) +
900–2000 m. +
curved +  and straight +
s--shaped +, clavate +, urceolate +, ovoid +, cylindric +, subcylindric +, lingulate +  and cup-shaped +
Steep limestone cliffs, gravelly slopes of gypseous clayey soils, desert scrub and Larrea communities. +
free +  and adnate +
cauline +  and basal +
apical +, subapical +  and inferior +
0 cm0 mm <br />0 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
2 cm20 mm <br />0.02 m <br /> (?) +
not well-differentiated +
inconspicuous +
connate +  and distinct +
5mm;11.5mm +
spreading +  and erect +
hairy +  and glabrous +
obovate +, oblanceolate +, elliptic +, ovate +  and spatulate +
0.3 cm3 mm <br />0.003 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
0 cm0 mm <br />0 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
Flowering May–Nov. +
J. Arnold Arbor. +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.45 cm4.5 mm <br />0.0045 m <br />) +
persistent +
lanceolate +  and narrowly ovate +
adnate +, free +  and distinct +
included +  and exserted +
15 +  and 45 +
0.4 cm4 mm <br />0.004 m <br /> (0.8 cm8 mm <br />0.008 m <br />) +
0 cm0 mm <br />0 m <br /> (50 cm500 mm <br />0.5 m <br />) +
papillate +
3-lobed +  and lingulate +
0.3 cm3 mm <br />0.003 m <br /> (0.75 cm7.5 mm <br />0.0075 m <br />) +
Mentzelia pachyrhiza +
Mentzelia sect. Mentzelia +
species +
dendritic +  and unbranched +
sinuous +