Corydalis decumbens (Thunberg) Persoon, Tuber rounded, 4-13 mm in diam.; new tubers arising directly on old tuber, mainly from axils of radical leaves. Stems usually several from each tuber, 10-25 cm, slender, weak, simple, with 2 or 3 leaves, without scales. Leaves twice to 3 × ternate; leaflet entire or deeply cut into subacute lobes. Raceme lax, 3-10-flowered; bracts ovate, 5-8 mm, entire. Pedicel 10-20 mm. Flowers nearly white or pale pink, sometimes marked with light blue, smelling like Viola odorata. Sepals caducous. Upper petal 14-18 mm, usually narrowly crested, with spreading limb; spur straight or slightly curved, distinctly shorter than limb; nectary 1/3-1/2 as long as spur, apex acuminate; lower petal broadly spatulate; inner petals with broad, rounded crests exceeding apex. Capsule linear, slightly torulose, 13-18 mm, 6-14-seeded. Seeds keeled, covered with vesicular papillae. Self-compatible. Fl. and fr. Feb-May. From the roots of Corydalis decumbens two new isoquinoline-type alkaloids, decumbenine B and C were isolated.