Silybum

Adanson
Fam. Pl. 2: 116, 605. 1763.
Common names: Milk thistle
Etymology: Greek silybon, a kind of thistle
Treatment appears in FNA Volume 19. Treatment on page 164. Mentioned on page 66, 82, 83.

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.

Distribution

Introduced; Mediterranean region.

Discussion

Species 2 (1 in the flora).

Selected References

None.

Lower Taxa