40. Thlaspi L. (penny cress)
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.
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.