28. Carduus L. (plumeless thistle)
Plants coarse,
biennial or less commonly annual, with stout taproots. Stems erect, usually
branched, noticeably spiny-winged, glabrous or finely hairy, sometimes
felty-hairy toward the tip. Leaves basal and alternate, sessile, the bases
decurrent into wings along the stem, these wavy or scalloped to evenly lobed,
spiny along the margins. Basal leaves in a dense, overwintering rosette, the
blades large, broadly elliptic to lanceolate or oblanceolate, deeply pinnately
lobed, the lobes somewhat irregular and also toothed to lobed, the margins
spiny, the surfaces glabrous or hairy. Stem leaves shallowly to deeply
pinnately lobed, occasionally nearly entire, elliptic to lanceolate or narrowly
oblong-elliptic or the margins spiny, the surfaces glabrous or hairy.
Inflorescences axillary and terminal, the heads long-stalked to nearly sessile,
solitary or in small clusters at the branch tips. Heads discoid, the involucre
cup-shaped to somewhat bell-shaped, the florets all appearing similar and
perfect. Receptacle flat or slightly convex, with numerous bristles. Involucral
bracts (except sometimes the innermost ones) tapered to a spiny tip. Pappus of
numerous long capillary bristles, these fused at the base, roughened with
minute, ascending barbs or teeth, shed more or less as a unit before fruiting.
Corollas reddish purple to purple, rarely white. Fruits appearing basally
attached, 2.5–4.0 mm long, oblong or slightly narrower at the symmetrical base,
somewhat flattened and sometimes slightly 4-angled in cross-section, the tip
usually with a slightly raised rim, the surface somewhat shiny, light brown to
grayish brown, with numerous longitudinal, darker brown stripes. About 90
species, Europe, Asia, Africa.