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 slender much branched herbs, with small alternate entire leaves, and small long-peduncled heads of both tubular and white or purple radiate flowers. Involucre narrowly campanulate, its bracts lanceolate, acute or acuminate, imbricated in few series, the outer slightly shorter. Receptacle small, naked. Ray-flowers in 1 row, pistillate. Disk-flowers perfect, or the central ones staminate, their corollas 5-lobed. Anthers obtuse and entire at the base. Style-branches narrow, flattened, their appendages short, obtuse. Achenes nearly terete, fusiform, or linear, 5-ribbed. Pappus usually of 5 rigid awn-like scabrous bristles, alternating with as many short scales or more. [Greek, bristle-pappus.]
Two known species, natives of the southwestern United States, the following typical. The genus Distasis DC. (Chaetopappa modesta A. Gray) is here regarded as distinct.
Chaetopappa asteroides DC. Prodr. 5: 301. 1836.
Pubescent, erect, 2'-12' high, the branches filiform. Lower and basal leaves spatulate, obtuse, 1/2'-1' long, petioled, the upper linear, much smaller and bractlike, sessile; heads about 3" broad; involucre about 2" high, its bracts scarious-margined, glabrous or nearly so; rays 5-12, raised on slender tubes; central sterile flowers usually awnless; shorter scales of the pappus of the fertile flowers hyaline, sometimes lacerate In dry soil, Missouri to Texas and northern Mexico. April-July.