2. Anthemis L. (chamomile)

Plants annual (perennial elsewhere), with taproots, weakly to more commonly strongly aromatic, sparsely to densely pubescent with somewhat appressed, sometimes 2-branched hairs. Stems erect or ascending, usually branched, finely ridged. Leaves alternate and basal (basal leaves sometimes withered by flowering time), sessile or short-petiolate with winged petioles and slightly broadened and more or less clasping bases. Leaf blades deeply 1–3 times pinnately lobed, hairy and glandular, the ultimate segments mostly linear to threadlike, sharply pointed at the tip, mostly 1-veined. Inflorescences of solitary heads at the branch tips, bractless or with a few reduced leaves well below the head. Heads radiate. Involucre cup-shaped to hemispheric, the bracts more or less in 2 or 3 loosely overlapping series, the outer ones somewhat shorter, elliptic-lanceolate to narrowly oblong or narrowly ovate-triangular, rounded to bluntly pointed at the tip, sparsely to moderately hairy, tan to brown, often with a narrow, green or brown midvein, the midrib not keeled, the margins broad, thin and papery, somewhat irregular to unevenly fringed. Receptacle hemispheric at flowering, elongating to conical or cylindrical at fruiting, solid, chaffy at least toward the center. Ray florets 10–20, pistillate or sterile, becoming reflexed after flowering, white, rarely pinkish-tinged. Disc florets perfect, numerous, the corolla yellow, rarely purplish-tinged, minutely glandular, the 5 lobes without resin canals, persistent, the tube often somewhat flattened toward the tip, becoming swollen at fruiting. Pappus absent or a very short collar or crown. Fruits oblong-obovoid to slightly wedge-shaped in profile, bluntly 4-angled to irregularly polygonal in cross-section, not flattened, truncate at the base, the tip often slightly obliquely truncate, strongly (8–)10-ribbed, the ribs rounded, smooth or appearing cross-wrinkled or with low tubercles, the surface otherwise glabrous or glandular, brown to dark brown. About 175 species, native of Europe, Asia, Africa, introduced nearly worldwide.

The genus Anthemis is treated here in a somewhat restricted sense, with the removal of the introduced A. tinctoria (and its foreign relatives) to the genus Cota. For further discussion, see the treatment of that genus.