| | 1. Petals 3–8 mm; stigma beyond anthers (see also G. heterozygum) |
| |
| | 2. Petals 4–8 mm; Sierra Nevada (s of Placer Co.) |
| G. eriospermum |
| | 2' Petals 3–7 mm; Cascade Range, San Bernardino Mountains, Warner Mountains, n High Sierra Nevada (Plumas Co.) |
| G. diffusum subsp. diffusum |
| | 1' Petals 0.5–3 mm; stigma not beyond anthers |
| |
| | 3. Seeds ± 50% aborted; fruit very irregular, lumpy |
| G. heterozygum |
| | 3' Seeds all maturing; fruit not irregular, slightly to very knobby |
| |
| | 4. Fruit flat; plant generally branched only below, 2° branches 0–few |
| |
| | 5. Lateral fruit valves staying attached; petals 0.8–1.5 mm; larger stamens ± 0.7 mm |
| G. humile |
| | 5' All fruit valves coming free; petals 1.3–1.8 mm; larger stamens 0.8–1.5 mm |
| G. racemosum |
| | 4' Fruit ± not flat; plant branched only above to throughout, 2° branches generally many |
| |
| | 6. Seeds in each chamber overlapped, generally in 2 rows |
| |
| | 7. Petals 0.7–1.5 mm; pedicel generally > fruit |
| G. ramosissimum |
| | 7' Petals 1.5–3 mm; pedicel generally < fruit |
| G. diffusum subsp. parviflorum |
| | 6' Seeds in each chamber not overlapped, in 1 row |
| |
| | 8. Seeds > 9, subopposite; fruit slightly knobby |
| |
| | 9. Branches ± throughout, generally 2–8 nodes between |
| G. decipiens |
| | 9' Branches at base or not, many above, generally 0–1 node between |
| G. diffusum subsp. parviflorum |
| | 8' Seeds (1)3–9, generally alternate; fruit very knobby |
| |
| | 10. Seeds 6–9; pedicel generally < fruit |
| G. diffusum subsp. parviflorum |
| | 10' Seeds (1)3–5; pedicel ± = fruit |
| G. oligospermum
|