Identification key to the subspecies of P. filifolia

1. Corolla white, angle between spur and corolla tube 99°–110°, spur conic 3.5–4.5 × 3–3.5 mm, seeds 339–509 µm long, without crests.......................................................................................................................................................... subsp. alba

- Corolla blue, violet or purple (rarely white), angle between spur and corolla tube 115°–140°, spur saccate 5.5–6.8 × 2.2– 2.8 mm, seeds 544–655 µm long, with crests ................................................................................................... subsp. filifolia