This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Annual or perennial, branching or scapose herbs, with alternate or basal, mostly pinnatifid leaves, and long-peduncled panicled or solitary heads of yellow or rarely white flowers. Involucre campanulate, its principal bracts in 1 or 2 series, equal or nearly so, with several series of shorter exterior ones. Receptacle flat, naked or bristly. Rays truncate and 5-toothed at the apex. Anthers sagittate at the base. Style-branches slender. Achenes oblong or linear, glabrous, 10-15-ribbed, 4 or 5 of the ribs usually more prominent than the others, truncate, or margined and 4-5-toothed at the summit. Pappus-bristles in 2 series, the inner naked or minutely serrulate, slender, coherent at the base and deciduous in a ring, the outer few (1-8), more persistent, or all deciduous in our species. [Greek, soft-hair, in allusion to the soft pappus.]
About 15 species, natives of the western and southwestern United States and lower California. Type species: Malacothrix calif ornica DC.
Malacothrix sonchoides T. & G. Fl. N. A. 2: 486. 1843.
Annual, glabrous throughout, or slightly glandular; stem branched, 6'-12' high. Leaves somewhat fleshy, oblong or linear-oblong in outline, pinnatifid and the lobes dentate with mucronate-pointed teeth, the basal ones 1 1/2'-3' long, narrowed into short broad petioles, those of the stem smaller, sessile; heads several or numerous, 8"-13" broad; principal bracts of the involucre linear, acute, scarious-margined, the outer short, oblong, obtuse, or acutish; achenes linear-oblong, margined at the summit by a 15-denticulate white border; pappus-bristles all deciduous.
On dry plains, western Nebraska and Kansas to California and Arizona. May-Aug.