| 1. Herbage ± glandular, sometimes sticky or strong-smelling |
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| 2. Plant ± sprawling; calyx minutely 35-toothed, obovoid, netted, tube enclosing fruit |
| C. multifidum |
| 2' Plant generally erect; calyx deeply 5-lobed, ± spheric, not netted, lobes generally folded over fruit |
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| 3. Inflorescence ± spheric, 36 mm diam, axillary; sepals yellow-glandular; seed generally vertical; longest leaves < 30 mm |
| C. pumilio |
| 3' Inflorescence spike or panicle-like, 10+ mm, sometimes terminal; sepals glabrous to short-stalked-glandular; seed generally horizontal; longest leaves 30120 mm |
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| 4. Inflorescence branches straight; flowers sessile; sepals glabrous to sparsely sessile-glandular; fruit wall free from seed |
| C. ambrosioides |
| 4' Inflorescence branches curved; flowers short-pedicelled; sepals densely short-stalked-glandular; fruit wall adherent to seed |
| C. botrys |
| 1' Herbage glabrous to minutely scaly or powdery, generally not strong-smelling |
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| 5. Perennial from stout, fleshy caudex; calyx tube generally > lobes in fruit |
| C. californicum |
| 5' Annual; calyx tube generally < lobes |
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| 6. Most seeds vertical; calyx lobes generally 3(4) horizontal seeds few, with 45 calyx lobes |
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| 7. Upper inflorescences axillary, ± spheric, < 10 mm diam |
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| 8. Lower leaf blades lanceolate to deltate, generally glabrous below; sepals thickened or ± fleshy in fruit |
| C. foliosum |
| 8' Lower leaf blades oblong to ovate, densely powdery below; sepals thin or membranous in fruit vertical and horizontal seeds generally ± equal in number |
| 2 C. glaucum |
| 7' Upper inflorescences axillary or terminal, spike-like, 15+ mm |
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| 9. Vertical seeds enclosed by calyx tube; style lobes ascending |
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| 10. Young leaves glabrous or sparsely powdery; calyx lobes abruptly pointed |
| C. chenopodioides |
| 10' Young leaves densely white-powdery; calyx lobes rounded to acute |
| C. macrospermum var. halophilum |
| 9' Vertical seeds subtended by calyx tube; style lobes spreading |
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| 11. Leaf densely powdery below; vertical & horizontal seeds often ± equal in number |
| 2 C. glaucum |
| 11' Leaf generally glabrous below; vertical seeds many more than horizontal |
| C. rubrum |
| 6' Most or all seeds horizontal; calyx lobes generally 5 |
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| 12. Leaf bright green, deeply 35-lobed, base truncate to cordate, tip acuminate to long-tapered; fruit 1.53 mm diam |
| C. simplex |
| 12' Leaf dull green to grayish, entire to toothed, base tapered to acute, tip rounded to acute; fruit generally < 1.5 mm diam |
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| 13. Lower leaf blades 1-veined from base |
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| 14. Lower leaf blades > 4 mm wide; calyx lobes strongly keeled in fruit; fruit wall free from seed, easily detached with dissecting needle |
| 2 C. desiccatum |
| 14' Lower leaf blades < 3.5 mm wide; calyx lobes weakly keeled in fruit; fruit wall adherent to seed, firm or fracturing when teased with dissecting needle |
| C. leptophyllum |
| 13' Lower leaf blades 3-veined from base |
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| 15. Fruit wall free from seed, easily detached with dissecting needle |
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| 16. Leaf length < 1.5 × width |
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| 17. Fruit top visible between calyx lobes; fruit 11.5 mm diam; leaf blade thin |
| C. fremontii |
| 17' Fruit top hidden by calyx lobes; fruit ± 1 mm diam; leaf blade thick, becoming ± leathery |
| C. incanum var. occidentale |
| 16' Leaf length generally 1.5+ × width |
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| 18. Stems several from base, branches ± dense; fruit ± 1 mm diam, top hidden by calyx lobes |
| 2 C. desiccatum |
| 18' Stems 1few from base, branches well spaced; fruit 11.5 mm diam, top visible between calyx lobes |
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| 19. Lower leaves entire, length 1.53 × width |
| C. atrovirens |
| 19' Lower leaves ± 12-lobed (-toothed), length 35 × width |
| C. pratericola |
| 15' Fruit wall adherent to seed, firm or fracturing when teased with dissecting needle |
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| 20. Stems mostly prostrate to ascending |
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| 21. Leaf blade oblong to lanceolate, length generally 2+ × width, base tapered; petiole < blade |
| C. carnosulum var. patagonicum |
| 21' Leaf blade widely elliptic to ovate, length < 1.5 × width, base obtuse to rounded; petiole ± = blade |
| C. vulvaria |
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| 22. Lower leaf blade generally entire or 12-toothed at base |
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| 23. Plant generally much-branched, ± wide; inflorescence often rounded in fruit; fruit < 1 mm diam |
| C. nevadense |
| 23' Plant generally few-branched, slender; inflorescence mostly spikes, ascending to erect; fruit 11.5 mm diam |
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| 24. Lower leaves narrowly lanceolate to elliptic; fruit ± 1 mm diam |
| C. hians |
| 24' Lower leaves ovate to ± deltate; fruit 11.5 mm diam |
| C. incognitum |
| 22' Lower leaf blade fewmany-toothed above base |
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| 25. Fruit wall surface minutely honeycombed at 20×; calyx lobes widely keeled in fruit |
| C. berlandieri |
| 25' Fruit wall surface smooth or irregularly rough at 20×; calyx lobes smooth to narrowly keeled |
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| 26. Leaf generally shiny dark green above, glabrous to sparsely powdery below; seed sharply angled at equator |
| C. murale |
| 26' Leaf dull green to grayish above, powdery below; seed obtusely angled or rounded at equator |
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| 27. Fruit top generally visible between calyx lobes; terminal inflorescence branches often stiffly ascending or erect; lower stem branches often decumbent |
| C. strictum var. glaucophyllum |
| 27' Fruit top generally hidden by calyx lobes; terminal inflorescence branches weak, sometimes pendent; lower stem branches 0 or generally ascending |
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| 28. Fruit 11.5 mm diam; leaf blade length < 1.5 × width; inflorescence branches generally straight |
| C. album |
| 28' Fruit ± 1 mm diam; leaf blade length generally 1.52 × width; inflorescence branches generally curved or pendent |
| C. missouriense
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