29. Chorizanthe rigida (Torrey) Torrey & A. Gray, Proc. Amer. Acad. Arts. 8: 198. 1870.
Acanthogonum rigidum Torrey in War Department [U.S.], Pacif. Railr. Rep. 4(5): 133. 1857
Plants erect, 0.2-0.8(-1.5) × 0.1-0.7(-1) dm, pubescent. Leaves basal and cauline; petiole 0.5-3(-4) cm; basal blade broadly elliptic to obovate, 0.5-2.5 × (0.3-)0.5-2 cm, thinly pubescent adaxially, more densely so to tomentose abaxially; proximal cauline leaf soon deciduous, 1, blade similar to basal leaf blades only 1-2(-2.5) × 0.5-1.5 cm, mucronate to awn-tipped, awn mostly 2-4 mm; distal cauline leaf blade persistent, 1 per node, sessile, blade linear to linear-lanceolate, 0.1-1.5 × 0.05-0.15 cm, becoming hard and thornlike with age. Inflorescences with involucres in dense clusters in axils of bracts, these on short shoots and each subtended by cauline leaves; bracts 2, subopposite to opposite, linear, 0.5-1(-1.2) cm × 1-2 mm, awns straight, 2-4 mm. Involucres 1, greenish, urceolate, 3-ribbed, 2-3 mm, corrugate, pubescent, rarely villous near base in some; teeth 3, unequal, with thickened anterior tooth toward base, 5-10 mm, sometimes expanding and becoming lanceolate to narrowly elliptic, others 0.5-1.2 mm; awns straight. Flowers 1-2, included to slightly exserted; perianth yellow, cylindric, 1.5-1.8 mm, densely pubescent abaxially; tepals connate ca. 2/ 3 their length, mono-morphic, oblong, rounded, entire apically; stamens 9, slightly exserted; filaments distinct, 0.5-1 mm, glabrous; anthers yellowish, ovate, 0.2-0.3 mm. Achenes brown, 3-gonous, (1.5-)1.8-2.2 mm. 2n = 38, 40.
Flowering Feb-Jun. Sandy to gravelly or rocky flats and slopes, desert scrub; -60-1900 m.; Ariz., Calif., Nev., Utah; Mexico (Baja California, Sonora).
Anyone with the misfortune to step bare-footed on Chorizanthe rigida after the plant has dried instantly appreciates its common name. The species is widespread on the Mojave and Sonoran deserts but only occasionally is it locally abundant or weedy. It is found also along the Lahontan Trough in western Nevada, a well-known biogeographic extension route north of the Mojave Desert (J. L. Reveal 1980). The exceedingly compact and dense inflorescences with suppressed secondary branches result in a series of leaves and bracts that subtend a closely arranged series of bracteated and involucrated flowers.