36. Rorippa Scop. (cress)

Plants annual, biennial, or perennial herbs, terrestrial or aquatic, glabrous or pubescent with unbranched hairs. Stems erect to spreading, unbranched or branched. Leaves alternate and sometimes also basal, short-petiolate or sessile, not clasping the stem or the petiole base with small, rounded auricles. Leaf blades simple or pinnately divided or compound. Inflorescences racemes or panicles with the lower branches sometimes subtended by reduced, leaflike bracts, the flowers bractless (with bracts elsewhere). Sepals ovate to narrowly oblong, erect or ascending, often green or yellowish. Petals not lobed, yellow (white in R. aquatica), sometimes absent. Stamens (4)6. Styles absent or 0.5–4.0 mm long. Fruits spreading or ascending, 1 or more times as long as wide, ovate to oblong or linear (circular elsewhere) in outline, circular in cross-section or nearly so or somewhat flattened at a right angle to the septum, straight or curved upward, the valves not veined or with a single, indistinct midnerve, dehiscent longitudinally. Ovules mostly in 2 rows in each locule. Seeds 5–100(–300) per locule. Seventy-five to 80 species, nearly worldwide.

Some species of Rorippa have been collected for use as a salad green or vegetable. While in Missouri in 1803 during the early days of their epic voyage, the Lewis and Clark Expedition collected some species of Rorippa along the Missouri River both for food and as a pressed specimen (Meehan, 1898; see also the introductory chapter on the history of floristic botany in Missouri in the first volume of the present work [Yatskievych, 1999]).