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1. Cauline leaf blade margins deeply pinnatifid to nearly pinnatisect. | P. sect. Dissecti |
1. Cauline leaf blade margins entire or toothed, rarely laciniate-pinnatifid. | → 2 |
2. Subshrubs or shrubs; staminodes glabrous; corollas pink, red, scarlet, or magenta, rarely lavender or violet. | → 3 |
3. Cauline leaf blades linear and pollen sacs explanate. | P. sect. Ambigui |
3. Cauline leaf blades obovate, ovate, oblanceolate, lanceolate, elliptic, or linear; pollen sacs navicular, saccate, subexplanate, or explanate. | → 4 |
4. Pollen sacs subexplanate to explanate, opposite; corollas weakly ventricose; thyrses cylindric; leaves glaucous. | P. sect. Petiolati |
4. Pollen sacs saccate or navicular, parallel or divergent; corollas salverform or funnelform; thyrses secund; leaves not glaucous. | → 5 |
5. Cauline leaf margins toothed or entire; corollas funnelform, glandular-pubescent internally abaxially and adaxially; cymes 1 per node; Texas. | P. sect. Baccharifolii |
5. Cauline leaf margins entire; corollas salverform, hairy internally abaxially; cymes 2 per node; Arizona, California, Colorado, Nevada, New Mexico, Utah. | P. sect. Bridgesiani |
2. Herbs, shrubs, or subshrubs; staminodes hairy distally or glabrous; corollas usually white, lavender, lilac, blue, violet, purple, ochroleucous, yellow, orange, or crimson, if pink, red, scarlet, or magenta, herbs and/or staminodes hairy, or both. | → 6 |
6. Pollen sacs saccate, dehiscing incompletely, distal 1/5–2/3 indehiscent, connectives splitting, rarely not. | → 7 |
7. Pollen sac sutures papillate; herbs. | P. sect. Penstemon |
7. Pollen sac sutures denticulate; herbs or subshrubs. | → 8 |
8. Herbs; pollen sac sides glabrous; staminodes glabrous, tips recurved; cauline leaf blade margins entire; thyrses interrupted. | P. sect. Chamaeleon |
8. Herbs or subshrubs; pollen sac sides glabrous or hairy; staminodes glabrous or hairy distally, tips straight; cauline leaf blade margins entire or toothed, rarely laciniate-pinnatifid; thyrses interrupted or continuous. | P. sect. Saccanthera |
6. Pollen sacs navicular, navicular-sigmoid, sigmoid, subexplanate, or explanate, dehiscing completely, if incompletely proximal 1/5–1/2 indehiscent and/or connectives not splitting. | → 9 |
9. Pollen sacs dehiscing incompletely, proximal 1/5–1/2 indehiscent and/or connectives not splitting. | → 10 |
10. Corollas red to scarlet or orange, rarely yellow, glabrous externally. | P. sect. Elmigera |
10. Corollas white to pink, lavender, lilac, blue, violet, or purple, glandular-pubescent or glabrous externally, if corollas reddish pink or rose red, glandular-pubescent externally. | → 11 |
11. Pollen sacs: connectives not splitting, sutures papillate, sides glabrous; corollas tubular-funnelform. | P. sect. Cristati |
11. Pollen sacs: proximal 1/5–1/3 indehiscent and/or connectives not splitting, sutures denticulate, sometimes papillate or smooth, sides glabrous or hairy; corollas funnelform, ventricose, or ventricose-ampliate. | P. sect. Glabri |
9. Pollen sacs dehiscing completely (rarely connectives not splitting in P. incertus). | → 12 |
12. Staminodes glabrous; pollen sacs parallel to divergent, sutures denticulate, teeth to 0.2–0.3 mm. | P. sect. Chamaeleon |
12. Staminodes hairy distally, sometimes glabrous; pollen sacs opposite or divergent, rarely parallel, sutures smooth, papillate, or denticulate, teeth to 0.1–0.2 mm. | → 13 |
13. Subshrubs; leaves cauline, rarely basal and cauline, blade margins entire; stems not glaucous; corollas 2-ridged abaxially. | P. sect. Caespitosi |
13. Herbs, shrubs, or subshrubs; leaves basal and cauline, sometimes basal few or absent, blade margins entire or toothed, if shrubs or subshrubs, leaves basal and cauline or leaf blade margins toothed or stems glaucous; corollas rounded to 2-ridged abaxially. | → 14 |
14. Stems and/or leaves and/or thyrse axes hairy; leaf blades not (or rarely) glaucous, not (or rarely) leathery. | → 15 |
15. Corollas glabrous externally, ventricose or ventricose-ampliate. | P. sect. Glabri |
15. Corollas glandular-pubescent externally, if glabrous then tubular, tubular-funnelform, or funnelform. | → 16 |
16. Corolla throats rounded abaxially, sometimes slightly 2-ridged; staminodes: distal (40–)50–100% hairy, hairs to 4 mm, exserted, sometimes reaching orifice or included, tips straight to recurved or coiled; seeds 1.4–4.8 mm, brown, dark brown, or black. | P. sect. Cristati |
16. Corolla throats slightly to prominently 2-ridged abaxially, rarely rounded; staminodes: distal 5–60(–90)% hairy, hairs to 3 mm, sometimes glabrous, included or reaching orifice, sometimes exserted, tips straight to recurved; seeds 0.4–2(–3.5) mm, tan, brown, gray, or black. | P. sect. Penstemon |
14. Stems, leaves, and thyrse axes glabrous, rarely scabrous; leaf blades glaucous, rarely not, leathery, rarely not. | → 17 |
17. Shrubs or subshrubs; stamen filaments: shorter pair glandular-puberulent proximally. | P. sect. Spectabiles |
17. Herbs; stamen filaments glabrous. | → 18 |
18. Leaf blade margins toothed. | P. sect. Spectabiles |
18. Leaf blade margins entire (rarely remotely and obscurely toothed in P. parryi). | → 19 |
19. Stamens exserted; corollas red, 32–36 mm. | P. sect. Coerulei |
19. Stamens included or longer pair reaching orifice, rarely exserted; corollas lavender to blue, violet, purple, white, pink, lilac, red, scarlet, crimson, magenta, orange, yellow, or ochroleucous, 6–33 mm. | → 20 |
20. Basal and proximal cauline leaf blades linear, 0.5–1.5 mm wide. | P. sect. Cristati |
20. Leaf blades ovate, obovate, lanceolate, oblanceolate, spatulate, trullate, oblong, or elliptic, rarely linear, 1–70 mm wide. | → 21 |
21. Pollen sacs 0.3–1.2 mm, opposite; corollas 7–22 mm, throats 2-ridged abaxially, sometimes rounded. | P. sect. Penstemon |
21. Pollen sacs 0.6–3 mm, opposite, divergent, or parallel; corollas 10–48 mm, throats rounded abaxially, rarely slightly 2-ridged. | → 22 |
22. Pollens sacs navicular; corollas glabrous externally, rarely obscurely glandular (P. carnosus). | P. sect. Coerulei |
22. Pollen sacs explanate, sometimes navicular; corollas glandular-pubescent externally, if glabrous staminode papillate distally, papillae to 0.2 mm. | P. sect. Gentianoides |
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