Monographs Details: Silybum
Authority: Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Description:Genus Description - Heads discoid, the fls all tubular and perfect; invol bracts imbricate, broad and firm, most of them spiny-margined and strongly spine-tipped; receptacle flat, densely setose; cors purple, with slender tube and long narrow lobes; filaments glabrous, connate at least below; anthers with a firm, slender, terminal appendage, shortly tailed at the base; style with an abrupt change of texture below the connate, papillate branches; achenes basifixed, somewhat compressed, glabrous; pappus of numerous slender, unequal, subpaleaceous bristles, deciduous in a ring; spiny winter-annual or biennial with alternate lvs and large, globose heads terminating the branches. 2, Mediterranean.