94. Omalotheca Cassini in F. Cuvier, Dict. Sci. Nat. ed. 2. 56: 218. 1828.
Guy L. Nesom
Perennials, 2–70 cm (fibrous-rooted, rhizomatous, not stoloniferous). Stems usually 1, erect (branched from bases or distally, woolly-tomentose to sericeous). Leaves basal (persistent in rosettes) and cauline; alternate; sessile; blades mostly narrowly lanceolate to oblanceolate, bases cuneate, margins entire, faces bicolor or concolor, abaxial white to gray, thinly tomentose, adaxial white to grayish and sericeous to thinly woolly or greenish and glabrate. Heads disciform, in spiciform or subcapitate arrays. Involucres campanulate to turbinate, 5–6 mm. Phyllaries in 2–3 series, stramineous to brownish (sometimes mottled; hyaline, stereomes not glandular), unequal, chartaceous toward apices. Receptacles flat to concave, smooth, epaleate. Peripheral (pistillate) florets 35–70+ (more numerous than bisexual); corollas purplish or whitish. Inner (bisexual) florets 3–4; corollas purplish or whitish, distally purplish or reddish. Cypselae obovoid to cylindric or fusiform, sometimes slightly compressed, faces strigillose (hairs not myxogenic, lengths 6–12 times diams.) and papillate (carpopodia forming minute stipes); pappi falling readily, of 15–25 distinct (falling separately) or basally connate (falling together), barbellate bristles in 1 series. x = 14.
Species 8–10 (3 in the flora): mostly Eurasian; three species reaching North America in native distribution (Omalotheca sylvatica perhaps not native, see below).
The species of Omalotheca have been placed in subg. Omalotheca (capitulescences of 1–10 heads, cypselae compressed-obovoid, and pappus bristles distinct and falling separately) and subg. Gamochaetiopsis Schultz-Bipontinus & F. W. Schultz (capitulescences of 10–100 heads, cypselae cylindric, and pappus bristles basally connate and falling together). In the flora, O. norvegica and O. sylvatica belong in subg. Gamochaetiopsis; O. supina is in subg. Omalotheca.
Nesom, G. L. 1990b. Taxonomic summary of Omalotheca (Asteraceae: Inuleae). Phytologia 68: 241–246.