40. Thlaspi L. (penny cress)

Plants annual, terrestrial, glabrous or nearly so, usually with an unpleasant odor when bruised or crushed. Stems mostly erect or ascending, unbranched below the inflorescence or several-branched from the base. Leaves alternate and sometimes also basal, sessile or short-petiolate, the bases clasping the stems with rounded or pointed auricles of tissue, simple, ovate, broadly elliptic, lanceolate, oblanceolate, or narrowly oblong, the margins entire or toothed. Inflorescences racemes or less commonly panicles, the flowers not subtended by bracts. Sepals erect or ascending, 1.0–3.5 mm long, oblong to ovate or elliptic, green, usually with white margins. Petals 2–5 mm long, unlobed or very shallowly notched at the tip, white. Stamens 6. Styles 0.1–0.3 mm long. Fruits spreading to broadly ascending, less than 3 times as long as wide, obovate to cordate or nearly circular in outline, strongly flattened at a right angle to the septum and sometimes inflated, the margins entire, but winged, the tip with a notch, dehiscent. Seeds 3–8 per locule. Six species, Europe, Asia.

Species of Thlaspi superficially resemble Lepidium campestre, especially when not in fruit. However, that species has densely hairy stems, whereas the Thlaspi species known to occur in the state thus far are glabrous. The species that Steyermark (1963) and many other North American botanists have called T. perfoliatum recently has been segregated into the genus Microthlaspi. See the treatment of that genus for further discussion.