| | 1. Seeds 2; leaf ± round in X-section |
| L. californicum |
| | 1' Seeds several–many; leaf ± flat to elliptic in X-section |
| |
| | 2. Calyx lobes 1/2 to > tube (or generally > 2 mm) |
| |
| | 3. Fruit firm, greenish purple or yellow to orange |
| |
| | 4. Herbage glandular-puberulent; fruit yellow to orange, with 2 cross-grooves above middle |
| L. cooperi |
| | 4' Stem glabrous, leaves glaucous; fruit greenish purple, not cross-grooved |
| L. pallidum var. oligospermum |
| |
| | 5. Filaments hairy at base, attached near middle of corolla tube; s Channel Islands, w Sonoran Desert |
| L. brevipes var. hassei |
| | 5' Filaments glabrous, attached near top of corolla tube; s Channel Islands |
| L. verrucosum |
| | 2' Calyx lobes < 2/3 tube (or generally < 2 mm) |
| |
| | 6. Central stems curved to arched, often unarmed; alien of waste places |
| L. barbarum |
| | 6' Stems generally stiffly spreading to ascending, generally thorny; natives |
| |
| | 7. Corolla lobes 1/3 to = tube |
| L. brevipes var. brevipes |
| | 7' Corolla lobes < 1/3 tube |
| |
| |
| | 9. Calyx 4–8 mm, lobes triangular, 1–2 mm |
| L. fremontii |
| | 9' Calyx 2.5–5 mm, lobes oblong-ovate, 2–4 mm |
| L. parishii |
| |
| | 10. Corolla lobe margin glabrous to finely straight-ciliate; leaf ± linear-oblanceolate |
| L. andersonii |
| | 10' Corolla lobe margin woolly-ciliate; leaf narrowly oblanceolate to obovate |
| L. torreyi
|