| | 1. Involucre with petal-like appendages on glands; stipules present, gland-like, minute |
| |
| | 2. Leaves opposite, margin finely toothed; annual; seed with a knob at tip |
| E. exstipulata var. exstipulata |
| | 2' Leaves alternate, margin entire; woody; seed without a knob |
| E. misera |
| | 1' Involucre without petal-like appendages on glands; stipules 0 |
| |
| | 3. Inflorescences few–many in cyme-like clusters at branch tips; involucre glands 1–3, cup-shaped |
| |
| | 4. Leaves alternate below, opposite above; involucre, fruit glabrous; seed ovoid |
| E. dentata |
| | 4' Leaves alternate throughout; involucre, fruit hairy; seed flattened |
| E. eriantha |
| | 3' Inflorescence clusters umbel-like below, cyme-like above; involucre glands 4, ± flat |
| |
| | 5. Leaves opposite, 4-ranked; fruit > 8 mm |
| E. lathyris |
| | 5' Leaves alternate; fruit < 6 mm |
| |
| | 6. Leaf margin finely toothed; gland margin entire or truncate |
| |
| | 7. Perennial; seed surface smooth or dotted |
| |
| | 8. Stem hairy; fruit tubercled |
| E. oblongata |
| | 8' Stem glabrous; fruit smooth |
| E. serrata |
| | 7' Annual; seed surface sculptured, net-like |
| |
| | 9. Fruit smooth — disturbed, waste places |
| E. helioscopia |
| E. spathulata |
| | 6' Leaf margin entire; gland horned or scalloped |
| |
| | 10. Leaves linear, sometimes oblanceolate; seed surface smooth |
| E. esula |
| | 10' Leaves obovate to ovate or elliptic; seed surface dotted or sculpture net-like |
| |
| | 11. Seed dotted; fruit 2-keeled on lobes — waste places, gardens |
| E. peplus |
| | 11' Seed sculpture low, net-like; fruit lobes smooth |
| |
| | 12. Annual (rarely biennial); gland horns thin, > gland width |
| E. crenulata |
| | 12' Perennial; gland horns thick, < gland width or 0 |
| |
| | 13. Gland hornless, margin scalloped |
| E. incisa |
| | 13' Gland 2-horned, margin entire to shallowly scalloped |
| E. palmeri
|