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..
Erect, hirsute or pubescent, branching herbs, with alternate, mostly dentate leaves, and rather large heads of both discoid and radiate yellow flowers, generally solitary at the ends of the branches. Involucre hemispheric or broadly campanulate, its bracts imbricated in several series, the outer shorter. Receptacle flat, alveolate. Ray-flowers pistillate. Disk-flowers perfect, or some of them only staminate. Style-branches flat, their appendages lanceolate or triangular. Achenes pubescent, obtuse, those of the ray-flowers thick, those of the disk-flowers flattened. Pappus of the ray-flowers obsolete or of a few caducous bristles, that of the disk-flowers of an inner row of numerous capillary rough bristles, and an outer row of shorter stouter bristles or scales. [Greek, different-case, from the dissimilar achenes.]
Five or 6 species, natives of the southern United States and Mexico, the following typical.
Inula subaxillaris Lam. Encycl. 3: 259. 1799.
Heterotheca Lamarckii Cass. Dict. Sci. Nat. 21: 131. 1821.
Biennial or sometimes annual, 1°-3° high. Basal and lower leaves petioled, ovate or oblong, 2'-3' long, the upper ones oblong, sessile or clasping, smaller, all acutish or obtuse, dentate; heads rather numerous, 6"-9" broad; involucre nearly hemispheric, 3"-S" high, its bracts linear, or slightly dilated above, the inner with scarious margins; rays 10-25; inner bristles of the pappus of the disk-flowers about 2" long.
In dry soil, Delaware to Florida, Louisiana, Kansas, Arizona and Mexico. In ballast, at Philadelphia. July-Sept.