Description from Flora of China
Chamaemelum Visiani (1845), not Miller (1754); Dibothrospermum Knaf; Rhytidospermum Schultz Bipontinus.
Herbs, annual or perennial; indumentum absent or of simple, basifixed hairs. Leaves 2- or 3-pinnatisect. Synflorescences cymose; capitula solitary or in ± flat-topped panicles, pedunculate, heterogamous or homogamous, radiate or discoid. Involucres hemispheric; phyllaries in 2-4 rows, scarious margins often narrow, white or pale to dark brown. Receptacle convex to conical, epaleate. Marginal florets in 1 row, female, lamina white or rarely pale pink. Disk florets bisexual; corolla tubular, apex 5-lobed; lobes each usually with resin sac. Anther bases obtuse, apical appendage ovate-triangular or oblong. Style branches with apex truncate. Achenes 3-angled, often wrinkled or tuberculate, with 1 adaxial and 2 lateral, and sometimes 1 or 2 abaxial, white ribs, abaxially and apically with (1 or)2(-5) distinct resin sacs. Corona present, sometimes forming an auricle, or with a few scales, sometimes absent.
Thirty-eight species: Europe and temperate Asia, a few species in N Africa and North America; five species (one endemic) in China.
(Authors: Shi Zhu (石铸 Shih Chu); Christopher J. Humphries, Michael G. Gilbert)