Fl. Bor.-Amer. 1: 69, plate 18, fig. A. 1830.
Annuals; not scapose; (glaucous), glabrous or pubescent. Stems erect, unbranched or branched distally. Leaves basal and cauline; petiolate or sessile; basal (often withered by anthesis or fruiting), not or, rarely, rosulate, shortly petiolate, blade margins subentire, dentate, pinnatifid, or pinnatisect [rarely entire]; cauline sessile, blade (base usually auriculate), margins entire, dentate, or pinnatifid to pinnatisect. Racemes (corymbose, several-flowered), considerably elongated in fruit. Fruiting pedicels often recurved, sometimes divaricate-ascending, slender. Flowers: sepals ascending, oblong to ovate, lateral pair not saccate basally; petals white to purplish, spatulate to oblong, (subequaling or longer than sepals), claw not differentiated from blade; stamens slightly tetradynamous; filaments slightly dilated basally; anthers ovate; nectary glands each side of lateral stamen or semi-annular, median glands absent. Fruits (pendulous), sessile, cymbiform, orbicular, obovate [ovate, elliptic], smooth, strongly latiseptate; valves each with prominent midvein, glabrous or pubescent; replum entire or crenate, often perforated, (winged, wing flattened, with radiating rays); septum obsolete; ovule 1 per ovary; style distinct (relatively short) or obsolete; stigma entire. Seeds aseriate, flattened, not winged, elliptical to orbicular; seed coat not mucilaginous when wetted; cotyledons accumbent.
w North America, nw Mexico.
Species 5 (4 in the flora).
Thysanocarpus erectus S. Watson occurs in northwestern Mexico on Cedros and Guadalupe islands and on the mainland of Baja California.
|1||Fruits cymbiform, wings strongly incurved (toward flat side of fruit); raceme internodes ca. 0.7-1.5(-2) mm in fruit.||Thysanocarpus conchuliferus|
|1||Fruits flat or plano-convex, wings not strongly incurved; raceme internodes (1.5-)2-18 mm in fruit||> 2|
|2||Fruiting pedicels weakly ascending, straight or nearly so (geniculately reflexed apically), 7-18 mm; fruits 7-10 mm wide, wings with distinct rays ± 0.1 mm wide.||Thysanocarpus radians|
|2||Fruiting pedicels smoothly recurved or straight and stiffly spreading, 2-7(-12) mm; fruits 2.5-6(-9) mm wide, wings with indistinct rays or (0-)0.2-0.5 mm wide||> 3|
|3||Cauline leaf blades lanceolate, widest at base, bases auriculate-clasping, auricles extending around stems (at least some leaves); basal leaf blade margins subentire to sinuate-dentate, never pinnatifid, surfaces often hirsute, sometimes glabrous.||Thysanocarpus curvipes|
|3||Cauline leaf blades linear to narrowly elliptic, widest near middle or equally wide throughout, bases not auriculate or inconspicuous auricles not extending around stems; basal leaf blade margins pinnatifid, sinuate-dentate, or subentire, surfaces usually glabrous, rarely sparsely hirsute.||Thysanocarpus laciniatus|