1. Corydalis aurea Willd. (golden corydalis)

Pl. 418 f; Map 1861

Plants green or more commonly gray and glaucous. Stems 10–35(–50) cm long, loosely to strongly ascending, often from a spreading base. Basal and lower stem leaves with the petiole 3–6 cm long, the upper leaves sessile or very short-petiolate. Leaf blades 1.5–10.0 cm long, with mostly 7–11 pinnae, these again 1 or 2 times deeply several-lobed, the ultimate segments linear or narrowly to occasionally broadly oblong-elliptic or lanceolate. Inflorescences extending past the foliage or not, all with open flowers, 5–30-flowered racemes. Flower stalks 2–4 mm long, ascending at flowering, ascending or pendant at fruiting. Corollas pale to bright yellow, the upper outer petal 13–18 mm long, the spur 4–9 mm long, straight or nearly so, the concave apical portion with a low, irregular crest or more often merely keeled. Fruits 15–30 mm long, straight or curved, glabrous, not appearing mealy. Seeds 1.8–2.1 mm long, the surface smooth or nearly so, the bluntly to sharply angled rim sometimes with a minute, raised ridge. 2n=16. March–June.

Uncommon, widely scattered, mostly south of the Missouri River (western U.S. east to North Dakota and Texas and eastward to Illinois, Pennsylvania, and New Hampshire; Canada, Mexico).

The last monographer of North American Corydalis, Gerald B. Ownbey (1947) did not include Missouri in the range of this species. He treated C. aurea as comprising two intergrading subspecies, with ssp. aurea occupying the western and northern portions of the overall range and ssp. occidentalis mainly in the southeastern portion of the species distribution. Steyermark (1963) apparently misinterpreted the characters separating C. aurea and its component subspecies from other Midwestern taxa of Corydalis, for he mapped abundant counties for each of them and also considered the taxa in the C. aurea complex to represent two separate species. Many of the specimens that Steyermark determined as C. aurea and C. montana have been annotated as C. micrantha by G. B. Ownbey and/or K. R. Stern. In his treatment for the Flora of North America Project, Kingsley R. Stern (1997a) adhered closely to the taxonomic scheme established by Ownbey (1947) but mapped a single disjunct Missouri locality for each of the two subspecies. For further discussion of present knowledge of the distributions of the two subspecies in Missouri, see the pertinent treatments below.