| |
| 2. Stem generally < 1 mm wide, solid; spikelet much wider than stem |
| 2 E. pachycarpa |
| 2' Stem 35 mm wide, spongy; spikelet ± as wide as stem |
| E. quadrangulata |
| 1' Stem round (sometimes flattened in pressing) |
| |
| 3. Fruit brownish to black, shiny tubercle hat-like, generally < 1/5 fruit body |
| |
| 4. Leaf tip whitish, membranous |
| E. thermalis |
| 4' Leaf tip green to reddish or becoming straw-colored, not membranous |
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| 5. Fruit ± 0.5 mm; tubercle base strongly narrowed |
| E. atropurpurea |
| 5' Fruit ± 0.71 mm; tubercle base barely narrowed |
| E. geniculata |
| 3. Fruit whitish to brown, shiny or dull |
| |
| 6. Style generally 2-branched; fruit 2-sided |
| |
| 7. Perennial, rhizomed; tubercle not flat, base narrowed; spikelet 525 mm, elongate, tip ± acute |
| E. macrostachya |
| 7' Annual, rhizome 0; tubercle flat, base not narrowed; spikelet 216 mm, oblong to ± round, tip ± obtuse |
| E. obtusa |
| 8. Tubercle < 1/4 fruit body; perianth bristles generally < fruit |
| var. engelmannii |
| 8' Tubercle 1/31/2 fruit body; perianth bristles > fruit |
| var. obtusa |
| 6' Style (2)3-branched; fruit (2)3-sided to round |
| |
| 9. Fruit longitudinal ridges generally > 3, crossbars many |
| |
| E. acicularis var. bella |
| |
| 11. Stem solid, generally < 0.5 mm wide, not flattened in pressing; flower bract with (reddish) brown stripes |
| E. acicularis var. acicularis |
| 11' Stem spongy, generally > 0.5 mm wide, often flattened in pressing; flower bract without (reddish) brown stripes |
| E. radicans |
| 9' Fruit longitudinal ridges 03, crossbars 0 |
| |
| 12. Spikelet 29-flowered |
| |
| 13. Stem generally 27 cm, not rhizomed; fruit 11.3 mm, generally = perianth bristles; spikelet 23.5 mm |
| E. parvula |
| 13' Stem generally 1040 cm, rhizomed; fruit 23 mm, generally < perianth bristles; spikelet 47 mm |
| E. quinqueflora |
| 12' Spikelet generally 10many-flowered |
| |
| 14. Flower bracts weakly 2-ranked; fruit tubercle base 3-lobed |
| 2 E. pachycarpa |
| 14' Flower bracts spiraled; fruit tubercle base ± round |
| |
| 15. Fruit ± 1.5 mm, tubercle flat; plant cespitose, rhizome short; spikelet 38 mm |
| E. bolanderi |
| 15' Fruit ± 13 mm, tubercle not flat; plant loosely cespitose, rhizome long; spikelet 320 mm |
| |
| 16. Fruit tubercle base not narrowed; stem tip often rooting to form new plant |
| E. rostellata |
| 16' Fruit tubercle base slightly narrowed; stem generally ascending, tip not rooting |
| |
| 17. Spikelet oblong to ovate, ± as wide as stem, tip obtuse to acute; perianth bristles 26, generally < fruit |
| E. montevidensis |
| 17' Spikelet linear-lanceolate to fusiform, much wider than stem, tip acute to acuminate; perianth bristles 67, generally > fruit |
| E. parishii
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