Heads essentially discoid, the fls yellow, all tubular and perfect except for a few inconspicuous marginal neutral ones with very slender, 2-3-lobed cor; invol of several series of broad, firm, spine-tipped bracts, the spines of the inner ones pinnatisect; receptacle flat, densely bristly; anthers with a firm, narrow, terminal appendage, shortly sagittate- tailed at the base; style with a ring of hairs and an abrupt change of texture at the base of the very short, scarcely divergent, papillate branches; achenes obliquely attached to the receptacle, subterete, strongly 20-ribbed, glabrous or sparsely hairy, with a firm, 10-toothed crown; pappus biseriate, the outer of 10 firm, smooth awns about as long as the achene, alternating with as many much shorter, minutely hairy and sparsely pectinate inner ones; prickly annuals with alternate, toothed or pinnatifid lvs, the heads terminating the branches, closely subtended by foliage lvs crowded beneath the proper invol. Monotypic.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
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