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 erect branching herbs, with alternate dentate or pinnatifid leaves, and small panicled slender-peduncled heads of yellow flowers. Involucre nearly cylindric, its principal bracts in 1 series, nearly equal, with a few exterior small ones at the base. Receptacle flat, naked. Rays truncate and 5-toothed at the apex. Anthers sagittate at the base. Style-branches slender. Achenes obovate-oblong, 20-30-nerved, somewhat flattened, narrowed below, rounded at the summit. Pappus none. [Greek, lampsana, the name of a crucifer.]
About 9 species, natives of the Old World, the following typical.
Lapsana communis L. Sp. Pl. 811. 1753.
Stem paniculately branched, glabrous above, more or less hispid-pubescent below, 1°-3 1/2° high. Lower leaves ovate, repand-dentate, obtuse, thin, pubescent, or glabrate, petioled, 2'-4' long, often with 2-6 lobes on the petiole, the uppermost oblong or lanceolate, sessile, acute, much smaller, mostly entire; heads very numerous, 3"-6" broad; involucre oblong-cylindric, 2"-3" high, and of about 8 linear glaucous principal bracts and several very small outer ones.
Along roadsides and in waste places, Quebec and Ontario to New Jersey, Pennsylvania and Michigan. Also on the Pacific Coast and in Jamaica. Naturalized from Europe. Called also bolgan-leaves, ballogan. June-Sept.