| | 1. Inflorescence thornless |
| |
| | 2. Flowers 2.5–5 mm, ± cleistogamous, keel-petal beakless |
| 2 P. californica |
| | 2' Some flowers > 7 mm, opening, keel-petal with a beak |
| |
| | 3. Beak of keel-petal oblong, generally notched or contorted, ± 0.7–1 mm diam near tip; aril glabrous; flower 9– 14.5 mm (sometimes 2.5–5 mm cleistogamous flowers also present near base) |
| 2 P. californica |
| | 3' Beak of keel-petal linear, entire, ± 0.2 mm diam near tip; aril hairy; flower 7–14 mm, of one type |
| P. cornuta |
| | 4. Flower 8.5–14 mm; wings densely puberulent; upper sepal generally acute to acuminate |
| var. cornuta |
| | 4' Flower 7–11.2 mm; wings glabrous, ciliate, or puberulent near tip; upper sepal generally rounded to obtuse |
| var. fishiae |
| | 1' Inflorescence thorn-tipped |
| |
| | 5. Flowers 2.5–5.3 mm; wings cream-colored or greenish; twigs densely hairy |
| |
| | 6. Pedicels, outer sepals, and leaves with spreading hairs |
| P. acanthoclada |
| | 6' Pedicels glabrous; outer sepals glabrous, ciliate, or sparsely hairy near tip; leaf hairs incurved or appressed |
| P. intermontana |
| | 5' Flowers 6–13.5 mm; wings pink; twigs glabrous or puberulent |
| |
| | 7. Beak of keel-petal with 1–2 prominent notches on lower side due to excess tissue; seeds more hairy at aril end |
| P. heterorhyncha |
| | 7' Beak of keel-petal entire or slightly jagged; seeds evenly hairy |
| P. subspinosa
|