| | 1. Perennial; anthers 0.5–1+ mm; spikelet axis breaking tardily above glumes and between florets |
| |
| | 2. Stems simple, erect, not weak or trailing; spikelets 1.5–2 mm wide; fruit > 1 mm |
| E. curvula var. curvula |
| | 2' Stems abruptly bent, branching, some becoming decumbent and rooting at nodes; spikelets ± 1 mm wide; fruit generally < 0.8 mm |
| E. lehmanniana |
| | 1' Annual; anthers generally 0.2–0.4 mm; spikelet axis not breaking apart, persistent, glumes and lemmas deciduous, paleas deciduous or remaining attached |
| |
| | 3. Stems widely creeping, rooting at nodes, forming mats |
| E. hypnoides |
| | 3' Stems often decumbent, not creeping, not mat-forming |
| |
| | 4. Fruit with one or both ends truncate; surface checkered, with an evident groove on side opposite embryo |
| E. mexicana |
| | 5. Spikelet ovoid to oblong, 1.5 mm + wide; fruit ± rectangular; inflorescence branches often with scattered glands |
| subsp. mexicana |
| | 5' Spikelet linear to linear-lanceolate, ± 1 mm wide; fruit pear-shaped; inflorescence not glandular |
| subsp. virescens |
| | 4' Fruit elliptic, ovate, or sometimes ± spheric, tip rounded; surface smooth, not grooved |
| |
| | 6. Plants without conspicuous glands or glandular areas |
| |
| | 7. Paleas deciduous; lower glume < 1/2 length of lowest floret; lowest inflorescence branches generally whorled |
| E. pilosa var. pilosa |
| | 7' Paleas persistent; lower glume > 1/2 length of lowest floret; inflorescence branches generally solitary or paired |
| E. pectinacea |
| | 8. Spikelet stalks spreading |
| var. miserrima |
| | 8' Spikelet stalks appressed to branches, diverging < 20° |
| var. pectinacea |
| | 6' Plants with conspicuous glands or glandular areas on leaf sheaths, blade margins, inflorescence axis and branches, spikelet stalks, or lemma keel |
| |
| | 9. Leaf blade margin with conspicuous glands; glume keel, lemmas, other plant parts also often glandular |
| |
| | 10. Spikelets 2.5–3 mm wide; spikelet stalk generally not glandular |
| E. cilianensis |
| | 10' Spikelets < 2 mm wide; spikelet stalks generally with 1 or 2 glands |
| E. minor |
| | 9' Leaf blade margin without glands; glume keel and lemmas not glandular |
| |
| | 11. Inflorescence axis with conspicuous glandular bands or patches especially below lowest branches; leaves without glands |
| E. barrelieri |
| | 11' Inflorescence axis without conspicuous glandular bands or patches, sometimes glandular below stem nodes; leaf sheath, blade with many circular glands |
| E. lutescens
|