Silybum Adans.
Family: Asteraceae
Silybum image

Annuals or biennials, taprooted, 15-300 cm, herbage glabrous, puberulent, or slightly tomentose, spiny. Stems erect, usually simple. Leaves basal and cauline; petiolate (basal and proximal cauline) or sessile (distal cauline); blades adaxially variegated, margins dentate and often coarsely pinnately lobed, teeth and lobes spine-tipped, glabrous or puberulent. Heads discoid, borne singly, terminal and in distal axils. ( Peduncles with reduced leaflike bracts.) Involucres ovoid to spheric, 15-60 mm diam. Phyllaries many in 4-6 series. unequal, outer and mid with appressed bases and spreading, lanceolate to ovate, spiny-fringed, terminal appendages, at least mid spine-tipped, innermost with erect, flat, entire, spineless apices. Receptacles flat, epaleate, covered with whitish bristles. Florets 25-100+; corollas pink to purple, tubes slender, distally bent, abruptly expanded into short throats, lobes linear; stamen filaments connate. anther bases sharply short-tailed, anther appendages oblong; style branches: fused portions with slightly swollen subterminal nodes, distally cylindric, distinct portions minute. Cypselae ovoid, slightly compressed, not ribbed, apices with smooth, entire rims, glabrous, basal attachment scars slightly angled; pappi falling in rings, outer of many minutely barbed, basally connate, subulate scales, inner of minute smooth bristles. x = 17.

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.

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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