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..
[Hymenatherum Cass. Bull. Soc. Philom. 1817: 12. 1817.]
Annual or perennial herbs, some species low undershrubs, with gland-dotted foliage and involucre, alternate or opposite leaves, and small heads of both tubular and radiate, mostly yellow flowers. Involucre campanulate, its principal bracts united into a cup, sometimes with smaller outer ones. Receptacle naked, or fimbrillate, not chaffy. Ray-flowers pistillate, fertile. Disk-flowers perfect, fertile. Style-branches truncate or blunt. Achenes striate. Pappus of several or numerous scales or bristles. [Greek, thyme-leaf, not applicable to the following species.]
About 15 species, natives of America. Besides the following, some 4 others occur in the western parts of the United States. Type species: Thymophylla setifolia Lag.
1849. Hymena herum aureum A. Gray, Proc. Am. Acad. 19:
Annual, glabrous, 4'-12' high, much branched; the leaves and involucre with large oval oil-glands. Leaves alternate, or the lower opposite, sessile or nearly so, very deeply parted into 5-9 linear-filiform, mostly entire, blunt segments; heads numerous, corymbose, 6"-10" broad, terminating the branches; involucre about 3" high, its bracts acute; rays about 12, 2 1/2"-3" long; pappus of 6-8 erose truncate scales, somewhat longer than the thickness of the achene.
Kansas and Colorado to Texas and New Mexico. June-Sept.