2. Anthemis L. (chamomile)
(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.