Arnica spp., arnica

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Intermountain Flora
Fibrous-rooted perennial herbs from a rhizome or caudex; leaves simple, opposite or the reduced uppermost ones occasionally alternate; heads rather large, turbinate to hemispheric, solitary to rather numerous at the ends of the branches or on axillary peduncles, yellow or orange, radiate or sometimes discoid, the rays pistillate and fertile, relatively few and broad; involucral bracts herbaceous, more or less eviddently biseriate, but subequal and connivent; receptable convex, naked; disk-flowers perfect and fertile; anthers entire or slgihtly sagittate at the base; style-branches flattened, truncate or very shortly appendiculate, penicillate, with ventromarginal stigmatic lines; achenes cylindric or nearly so, 5- to 10-ribbed; pappus of numerous white to tawny, barbellate or subplumose capillary bristles; x = 19. Many of the species are partly or wholly apomictic; the polyploid forms are thought to be always apomictic.

Cronquist, A., Holmgren, A.H., Holmgren, N.H., Reveal, J.L., and Holmgren, P.K. (1994) "Intermountain Flora" pgs. 91-92, vol. 5, The New York Botanical Garden New York.