| 1 |
Petals white |
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(2) |
| + |
Petals light to golden yellow |
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(7) |
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| 2 (1) |
Anther epidermis papillate |
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(3) |
| + |
Anther epidermis smooth |
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(5) |
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| 3 (2) |
Leaf blade widest intersinus distances 9.5–29 mm. |
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1 Mentzelia hualapaiensis (in part) |
| + |
Leaf blade widest intersinus distances 0.8–9.1 mm |
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(4) |
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| 4 (3) |
5 outermost stamens without anthers; New Mexico, Texas. |
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2 Mentzelia humilis |
| + |
5 outermost stamens with anthers; Arizona. |
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3 Mentzelia canyonensis |
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| 5 (2) |
Petals 13–22.7 mm wide; stamens white to yellow. |
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4 Mentzelia decapetala |
| + |
Petals 1.9–10.3 mm wide; stamens white |
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(6) |
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| 6 (5) |
Petals 22.6–49 × 3.6–10.3 mm; bracts pinnate. |
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5 Mentzelia nuda |
| + |
Petals 14.7–22(–24.4) × 1.9–4.4 mm; bracts entire or dentate. |
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6 Mentzelia strictissima |
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| 7 (1) |
Petals hairy abaxially |
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(8) |
| + |
Petals glabrous abaxially |
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(10) |
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| 8 (7) |
Branches perpendicular to stem, especially proximal and mid-stem, or slightly antrorse, especially distal, ± equal; Montrose County, Colorado. |
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7 Mentzelia paradoxensis |
| + |
Branches antrorse, proximal longer than distal, all usually extending to near the distal end of plant; Arizona, Colorado (including Montrose County), New Mexico, Utah |
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(9) |
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| 9 (8) |
5 outermost stamens with anthers; margins of proximal leaf blades with teeth 0.5–4 mm; Colorado. |
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8 Mentzelia marginata |
| + |
5 outermost stamens usually without anthers; margins of proximal leaf blades with teeth or lobes 1.2–6(–9) mm, always some more than 4 mm; Arizona, Colorado, New Mexico, Utah. |
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9 Mentzelia cronquistii |
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| 10 (7) |
Anther epidermis papillate |
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(11) |
| + |
Anther epidermis smooth |
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(16) |
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| 11 (10) |
5 outermost stamens with anthers |
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(12) |
| + |
5 outermost stamens without anthers |
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(13) |
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| 12 (11) |
Leaf blades 4–12.2 mm wide, always some more than 10 mm wide, margins usually entire, rarely dentate, teeth 0(–4), 0.1–1.4 mm; seed coat cell papillae 3–5 per cell; Utah. |
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10 Mentzelia argillosa |
| + |
Leaf blades 1.5–8.8 mm wide, margins entire, dentate, or pinnate, teeth or lobes 0–8 (always some leaves with 5+ teeth or lobes), 0.1–2 mm (always some more than 1.4 mm); seed coat cell papillae 5–8 per cell; Nevada. |
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11 Mentzelia argillicola |
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| 13 (11) |
Leaf blade widest intersinus distances 9.5–29 mm. |
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1 Mentzelia hualapaiensis (in part) |
| + |
Leaf blade widest intersinus distances 1–4.2 mm |
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(14) |
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| 14 (13) |
Second whorl of stamens without anthers. |
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12 Mentzelia perennis |
| + |
Second whorl of stamens with anthers |
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(15) |
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| 15 (14) |
Seed coat anticlinal cell walls straight, papillae 38–45 per cell; Texas. |
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13 Mentzelia saxicola (in part) |
| + |
Seed coat anticlinal cell walls sinuous, papillae 6–12 per cell; New Mexico. |
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14 Mentzelia todiltoensis |
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| 16 (10) |
Capsules longitudinally ridged. |
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15 Mentzelia rusbyi |
| + |
Capsules not longitudinally ridged |
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(17) |
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| 17 (16) |
Stems multiple, from subterranean branching caudices |
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(18) |
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Stems solitary or, if multiple, from ground-level caudices |
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(31) |
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| 18 (17) |
5 outermost stamens without anthers. |
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16 Mentzelia springeri |
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5 outermost stamens with anthers |
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(19) |
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| 19 (18) |
Bases of distal leaf blades clasping |
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(20) |
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Bases of distal leaf blades not clasping |
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(22) |
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| 20 (19) |
Leaf blade surfaces densely hairy, whitish, abaxial surfaces with complex grappling-hook and needlelike trichomes; Ash Meadows, Nye County, Nevada. |
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17 Mentzelia leucophylla |
| + |
Leaf blade surfaces moderately hairy, green, abaxial surfaces with complex grappling-hook trichomes only; se California and s Nevada (including Nye County) |
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(21) |
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| 21 (20) |
Leaf blades 5.8–9.1 mm wide, widest intersinus distances 4.6–7.1 mm; margins of distal leaf blades with 0–6 teeth; seed coat cell papillae 15–46 per cell. |
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18 Mentzelia tiehmii |
| + |
Leaf blades 7.6–41.2 mm wide, widest intersinus distances 5.1–35.3 mm; margins of distal leaves with 6–16 teeth; seed coat cell papillae 6–17 per cell. |
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19 Mentzelia oreophila |
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| 22 (19) |
Margins of proximal leaf blades 3-fid or pinnate to pinnatisect (rarely entire in M. librina) |
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(23) |
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Margins of proximal leaf blades entire or dentate to serrate |
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(26) |
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| 23 (22) |
Filaments of 5 outermost stamens broadly spatulate, strongly clawed |
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(24) |
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Filaments of 5 outermost stamens narrowly spatulate or oblanceolate, slightly clawed |
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(25) |
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| 24 (23) |
Margins of proximal leaf blades pinnate to pinnatisect, lobes 4–12. |
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20 Mentzelia uintahensis |
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Margins of proximal leaf blades usually 3-fid, rarely entire or pinnate, teeth or lobes usually 2, rarely 0 or 4. |
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21 Mentzelia librina |
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| 25 (23) |
Petals 2.9–3.8 mm wide; filaments of 5 outermost stamens less than 1.3–1.9 mm wide; Utah. |
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22 Mentzelia flumensevera |
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Petals 5.1–9 mm wide; filaments of 5 outermost stamens 2–4.5 mm wide; Colorado. |
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23 Mentzelia multicaulis |
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| 26 (22) |
Stems glabrescent, smooth to the touch. |
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24 Mentzelia polita |
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Stems hairy |
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(27) |
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| 27 (26) |
Margins of proximal leaves entire |
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(28) |
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Margins of proximal leaf blades dentate or serrate, with 4–12 teeth |
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(29) |
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| 28 (27) |
Petals 7.4–11 × 2.6–3.4 mm; margins of distal leaf blades entire; filaments of 5 outermost stamens slightly clawed; Arizona. |
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25 Mentzelia memorabilis |
| + |
Petals 12.5–17.2 × 6.1–11.2 mm; margins of distal leaf blades entire or dentate; filaments of 5 outermost stamens strongly clawed; Colorado. |
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26 Mentzelia rhizomata |
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| 29 (27) |
Petals 6.7–9.2 mm wide; seed coat cell papillae 11–15 per cell. |
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27 Mentzelia goodrichii |
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Petals 2.3–5.9 mm wide; seed coat cell papillae 3–6 per cell |
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(30) |
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| 30 (29) |
Stems zigzag; margins of proximal leaf blades with 4–6 teeth, each 0.5–0.6 × 1.2–1.5 mm. |
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28 Mentzelia shultziorum |
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Stems straight; margins of proximal leaf blades with 8–12 teeth, each 1–4 × 1.7–6 mm. |
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29 Mentzelia puberula |
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| 31 (17) |
5 outermost stamens not petaloid, with anthers, filaments linear to narrowly elliptic or narrowly spatulate, 0.5–2(–2.5) mm wide, if narrowly spatulate, to 1.5 mm wide |
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(32) |
| + |
5 outermost stamens petaloid, with or without anthers, filaments narrowly spatulate to elliptic or oblanceolate, 1–9.7 mm wide, if narrowly spatulate and less than 1.5 mm wide, then without anthers |
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(34) |
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| 32 (31) |
Petals 23.5–70 mm; styles 20.4–57 mm; 5 outermost stamens 17.7–55 mm. |
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30 Mentzelia laevicaulis |
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Petals (6.1–)7.3–15.8(–18) mm; styles 3.7–13 mm; 5 outermost stamens 4–13.2 mm |
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(33) |
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| 33 (32) |
Petals 11.7–15.8(–18) mm; 5 outermost stamens 10.2–13.2 mm. |
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31 Mentzelia inyoensis |
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Petals (6.1–)7.3–10 mm; 5 outermost stamens 4–8 mm. |
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32 Mentzelia candelariae |
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| 34 (31) |
Margins of distal leaf blades pinnatisect (sometimes pinnate in M. laciniata) |
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(35) |
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Margins of distal leaf blades entire, dentate, serrate, or pinnate |
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(39) |
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| 35 (34) |
Petals 30–42.2 mm; 5 outermost stamens 27–37.4 mm; styles 24–32.4 mm. |
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33 Mentzelia conspicua |
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Petals 8.3–23.8(–26) mm; 5 outermost stamens 6.5–20.4 mm; styles 6.1–12.5(–14) mm |
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(36) |
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| 36 (35) |
Petals 8.3–13 mm; 5 outermost stamens 6.5–10.7 mm; Colorado, Nevada, Utah. |
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34 Mentzelia lagarosa |
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Petals 13–23.8(–26) mm; 5 outermost stamens 10.2–20.4 mm; Arizona, Colorado, New Mexico |
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(37) |
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| 37 (36) |
Lobes of distal leaf blades strongly antrorse; branches upcurved; Arizona, New Mexico. |
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35 Mentzelia holmgreniorum |
| + |
Lobes of distal leaf blades slightly antrorse or perpendicular to leaf axis; branches straight; Arizona, Colorado, New Mexico |
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(38) |
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| 38 (37) |
Seed coat cell papillae 42–48 per cell; Chuska Mountains of Arizona and New Mexico. |
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36 Mentzelia filifolia |
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Seed coat cell papillae 5–14 per cell; Colorado, New Mexico (not Chuska Mountains). |
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37 Mentzelia laciniata |
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| 39 (34) |
Bases of distal leaf blades clasping (rarely a few not clasping in M. pterosperma) |
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(40) |
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Bases of distal leaf blades not clasping (sometimes a few clasping in M. mexicana) |
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(41) |
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| 40 (39) |
Capsules cup-shaped; Arizona, California, Colorado, Nevada, Utah. |
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38 Mentzelia pterosperma |
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Capsules cylindric; Kansas, Missouri, Oklahoma, Texas. |
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39 Mentzelia albescens |
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| 41 (39) |
Filaments of 5 outermost stamens strongly clawed; on black (to sometimes reddish) volcanic cinder cone soils in San Francisco Volcanic Field, Coconino County, Arizona. |
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40 Mentzelia collomiae |
| + |
Filaments of 5 outermost stamens slightly clawed; not on black (to sometimes reddish) volcanic cinder cone soils in San Francisco Volcanic Field, Coconino County, Arizona |
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(42) |
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| 42 (41) |
Seed coat cell anticlinal walls straight |
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(43) |
| + |
Seed coat cell anticlinal walls wavy to sinuous |
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(47) |
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| 43 (42) |
Capsule length more than 2 times diam. (occasionally a few slightly less in M. reverchonii) |
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(44) |
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Capsule length to 2 times diam. (sometimes a few more in M. longiloba) |
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(45) |
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| 44 (43) |
Styles 8.7–11.4(–13) mm; Colorado, New Mexico, Oklahoma, Texas. |
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41 Mentzelia reverchonii |
| + |
Styles 5.6–7.8 mm; Montana, Utah, Wyoming. |
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42 Mentzelia pumila |
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| 45 (43) |
Capsule bases tapering; seed coat cell papillae 4–6 per cell. |
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43 Mentzelia longiloba (in part) |
| + |
Capsule bases rounded; seed coat cell papillae 8–45 per cell |
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(46) |
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| 46 (45) |
Seed coat cell papillae 8–12 per cell; leaf blade widest intersinus distances 3.4–19 mm. |
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44 Mentzelia mexicana |
| + |
Seed coat cell papillae 38–45 per cell; leaf blade widest intersinus distances 1.6–3.4 mm. |
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13 Mentzelia saxicola (in part) |
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| 47 (42) |
Margins of proximal leaves with 4–12 teeth or lobes |
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(48) |
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Margins of proximal leaves with 14–38 teeth or lobes (occasionally 10–38 in M. speciosa) |
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(49) |
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| 48 (47) |
Plants candelabra-form; proximal branches not decumbent; largest leaf trichomes with pearly white bases; leaf blade margin teeth with proximal side antrorse, distal side perpendicular to leaf axis; Arizona, Nevada, Utah. |
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45 Mentzelia integra |
| + |
Plants bushlike; proximal branches decumbent; largest leaf trichomes without pearly white bases; leaf blade margin teeth or lobes perpendicular to leaf axis; c Colorado. |
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46 Mentzelia densa |
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| 49 (47) |
Seed coat cell anticlinal walls wavy; petals golden yellow; leaf blades 43.6–233 mm, always some 146+ mm. |
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47 Mentzelia speciosa |
| + |
Seed coat cell anticlinal walls sinuous; petals light to golden yellow; leaf blades 32.8–125(–146) mm |
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(50) |
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| 50 (49) |
5 outermost stamens with anthers |
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(51) |
| + |
5 outermost stamens without anthers |
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(52) |
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| 51 (50) |
Leaf blade widest intersinus distances 2.3–7.1 mm, always some leaves 4+ mm; branches upcurved. |
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43 Mentzelia longiloba (in part) |
| + |
Leaf blade widest intersinus distances 1–2.9 mm; branches straight. |
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48 Mentzelia sivinskii |
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| 52 (50) |
Leaf blade widest intersinus distances 1–3.9 mm; petals light yellow. |
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49 Mentzelia procera |
| + |
Leaf blade widest intersinus distances 2.1–13.7(–14) mm, always some leaves 4+ mm; petals light to golden yellow |
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(53) |
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| 53 (52) |
Seed coat cell papillae 10–21 or 67–106 per cell; Arizona, California, Colorado, New Mexico, Utah. |
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43 Mentzelia longiloba (in part) |
| + |
Seed coat cell papillae 29–48 per cell; Colorado, Nebraska, New Mexico, Wyoming |
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(54) |
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| 54 (53) |
Branches distal or along entire stem, straight. |
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50 Mentzelia chrysantha |
| + |
Branches distal, upcurved. |
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51 Mentzelia multiflora |
