Trans. Amer. Philos. Soc., n. s.7: 312. 1840
c United States, Mexico.
Species 12 (3 in the flora).
Astranthium is characterized by its herbaceous habit, heads borne singly on long peduncles, subequal phyllaries in 2–3 series, conic receptacles, white or blue rays, tubular disc corollas, and flattened, papillate cypselae with coroniform or no pappi. Apically glochidiate cypsela hairs have each apical cell abruptly reflexed in opposite directions. The species are separated by small but consistent morphologic differences, often accompanied by differences in chromosome number. All but three of the species are known only from Mexico (D. C. D. De Jong 1965; J. Rzedowski 1983).
Vegetatively and florally, Astranthium is similar to the monotypic Dichaetophora, which has the same chromosome number (2n = 6) as northern species of Astranthium. Epappose species of Erigeron may be superficially similar to Astranthium (D. C. D. De Jong and G. L. Nesom 1982); they are distantly related.
|1||Plants fibrous-rooted; cypsela faces glabrous or glochidiate-hairy only distally||Astranthium integrifolium|
|1||Plants taprooted; cypsela faces uniformly glochidiate-hairy||> 2|
|2||Ray florets (7–)13–24; disc corollas 2–3 mm; cypselae 1–1.6 × 0.6–0.8 mm, faces minutely striate, otherwise nearly smooth, rarely papillate-pebbly||Astranthium ciliatum|
|2||Ray florets 18–35; disc corollas 3.2–3.8 mm; cypselae 1.4–2.1 × 0.7–1.2 mm, faces minutely, glandular-papillate-pebbly||Astranthium robustum|