| 1. Plant prostrate or decumbent, producing roots, juvenile leaves at nodes; heads in racemes |
| E. racemosum |
| 1' Plant decumbent to erect, not rooting at nodes; heads in cymes |
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| 2. Plant densely, finely hairy throughout; heads 57-flowered |
| E. constancei |
| 2' Plant glabrous (rarely sparsely hairy on leaves only); heads > 10-flowered |
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| 3. Heads bright blue or purple; bractlets generally regularly 3-toothed at tip |
| E. articulatum |
| 3' Heads greenish white, sometimes faintly bluish; bractlets entire to deeply pinnately lobed but not regularly 3-toothed at tip |
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| 4. Bracts and bractlets very rigid, margins generally entire, prominently thickened |
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| 5. Inflorescence as a whole yellowish green; leaf generally sharply serrate to irregularly cut; coastal |
| E. armatum |
| 5' Inflorescence as a whole silvery green; leaf pinnately sharply lobed; n&c Sierra Nevada Foothills |
| E. pinnatisectum |
| 4' Bracts and bractlets ± flexible, margin generally sharply toothed, not thickened |
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| 6. Bracts similar to bractlets, spines on outer side dense |
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| 7. Leaf blades deeply pinnately lobed, >> petiole; Great Central Valley, adjacent foothills |
| E. castrense |
| 7' Leaf blades sharply serrate to sharply lobed, > petiole; Modoc Plateau |
| E. mathiasiae |
| 6' Bracts unlike bractlets, spines on outer side 0 or few |
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| 8. Sepals pinnately sharply lobed or sharply toothed; s Great Central Valley, c&s Sierra Nevada Foothills |
| E. spinosepalum |
| 8' Sepals generally entire; North Coast Ranges, High Cascade Range, San Francisco Bay Area, South Coast Ranges, South Coast, Modoc Plateau |
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| 9. Main stem 0, plant branching or spreading directly from basal rosette; basal leaves generally > branches; fruit scales subequal; High Cascade Range, Modoc Plateau |
| E. alismifolium |
| 9' Main stem branching 15 cm above basal rosette; basal leaves generally < branches; fruit scales generally unequal; North Coast Ranges, Great Central Valley, San Francisco Bay Area, South Coast Ranges, South Coast |
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| 10. Petiole < leaf blade; fruit scales obtuse |
| E. vaseyi |
| 10' Petiole generally > leaf blade; fruit scales acuminate |
| E. aristulatum |
| 11. Styles in fruit >> calyx; North Coast Ranges, San Francisco Bay Area |
| var. aristulatum |
| 11' Styles in fruit ± = calyx; San Francisco Bay Area, South Coast Ranges, Southwestern California |
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| 12. Plant stout, ascending or erect; bractlets sharply toothed |
| var. hooveri |
| 12' Plant weak, spreading; bractlets entire |
| var. parishii
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