112. Tanacetum Linnaeus, Sp. Pl. 2: 843. 1753; Gen. Pl. ed. 5, 366. 1754.
Tansy, tanaisie [Derivation unknown; possibly Greek athanasia, immortality, through Medieval Latin tanazita]
Linda E. Watson
Perennials [annuals, subshrubs], 5–150 cm (usually rhizomatous; usually aromatic). Stems 1 or 2–5+, erect or prostrate to ascending, branched proximally and/or distally, glabrous or hairy (hairs basifixed and/or medifixed, sometimes stellate). Leaves basal and/or cauline; alternate; petiolate or sessile; blades mostly obovate to spatulate, usually 1–3-pinnately lobed, ultimate margins entire, crenate, or dentate, faces glabrous or hairy. Heads usually radiate, sometimes disciform (or quasi-radiate or -radiant), usually in lax to dense, corymbiform arrays, rarely borne singly. Involucres mostly hemispheric or broader, (3–)5–22+ mm diam. Phyllaries persistent, (20–)30–60+ in (2–)3–5+ series, distinct, ± ovate to oblong or oblong to lanceolate or lance-linear (sometimes carinate), unequal, margins and apices (pale to dark brown or blackish) scarious (tips sometimes dilated). Receptacles flat to conic or hemispheric (sometimes hairy), epaleate. Ray florets usually 10–21+ (pistillate and fertile or neuter; corollas pale yellow to yellow or white, usually with yellowish bases [pink], laminae oblong to flabellate), sometimes 0 (in disciform or quasi-radiate or -radiant heads, peripheral pistillate florets 8–30+; corollas pale yellow, ± zygomorphic, lobes 3–4, sometimes ± raylike). Disc florets 60–300+, bisexual, fertile; corollas yellow, tubes ± cylindric, throats narrowly funnelform to campanulate, lobes (4–)5, ± deltate. Cypselae obconic or ± columnar (circular in cross section), ribs (4–)5–10(–12+), faces usually gland-dotted, sometimes glabrous (pericarps without myxogenic cells or resin sacs, embryo sac development tetrasporic); pappi usually coroniform, rarely 0 [distinct scales or each pappus an adaxial auricle]. x = 9 (polyploidy).
Species 160 (4 in the flora): North America, Europe, Asia, n Africa; some species widely cultivated.
