Tribe 1. CARDUEAE (CYNAREAE) - thistle tribe (Source: Johnson
and Iltis 1963; Gleason and Cronquist, 1991; FNA, 2006; edited
by R. R. Kowal, 2006 July 24.) 1. Neither plants nor heads
prickly OR phyllaries spine-tipped and corollas yellow; achenes
obliquely attached to the receptacle; marginal disk florets
often enlarged and showy; phyllaries often with margins scarious
and deeply cleft at tip (laciniate); pappus hairs mostly less
than 3 mm long or lacking ......... CENTAUREA - star-thistle. 1.
Plants and/or heads prickly; corollas not yellow; achenes
attached by the base to the receptacle; florets all alike;
phyllaries not laciniate at tip; pappus hairs usually more than
5 mm long. 2. Leaves unarmed, broadly rounded at base; tip of
phyllary a hook ......... ARCTIUM - burdock. 2. Leaves prickly,
lanceolate to ovate; tip of phyllary a straight spine or merely
mucronate. 3. Heads 1-flowered, aggregated into globose
secondary heads ......... ECHINOPS - globe-thistle. 3. Heads
many-flowered, only rarely sessile.