13. Cardamine L. (bitter cress)

Plants annual, biennial, or perennial herbs, terrestrial or occasionally emergent aquatics (in C. bulbosa), glabrous or pubescent with unbranched hairs. Stems 10–30 cm long (longer elsewhere), erect or ascending, unbranched or few-branched. Leaves alternate, opposite, or whorled and often also basal, simple, trifoliate, or pinnately or palmately compound, the margins entire or toothed, the bases not clasping. Inflorescences racemes or less commonly few-branched panicles, the flowers not subtended by bracts. Sepals lanceolate to narrowly elliptic or oblong, erect or ascending. Petals 7–19 mm (or more) long, not lobed, white, pink, or purple. Stamens 6, rarely reduced to 4. Fruits erect or ascending, usually more than 10 times as long as wide, straight, flattened parallel to the septum, usually tapered toward the tip into the style, the replum narrowly winged, the valves unveined or with a faint midnerve, longitudinally dehiscent. Seeds in 1 row in each locule. About 200 species, worldwide.

The present circumscription of the genus includes species formerly segregated from Cardamine as the genus Dentaria by many North American authors, including Steyermark (1963). However, within the context of variation in Cardamine throughout the world, none of the characters thought to separate the two groups can be applied consistently or reliably (Al-Shehbaz, 1988a, b). Thus, although these species appear amply distinct when compared to other Missouri taxa, they are best maintained taxonomically as part of an expanded concept of Cardamine. This expanded concept has become widely accepted in recent years (Rollins, 1993; Appel and Al-Shehbaz, 2002) and is supported by extensive molecular data (Franzke et al., 1998; Sweeney and Price, 2000).