Omalotheca

Cassini in F. Cuvier

in F. Cuvier, Dict. Sci. Nat. ed. 2, 56: 218. 1828

Etymology: Greek omalo, even or equal, and theke, container, envelope, or sheath, perhaps alluding to involucres
Treatment appears in FNA Volume 19. Treatment on page 438. Mentioned on page 58, 387, 429, 439.
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.

Distribution

Mostly Eurasian, three species reaching North America in native distribution (Omalotheca sylvatica perhaps not native, see below).

Discussion

Species 8–10 (3 in the flora).

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.

Lower Taxa

Key

1 Plants 2–8(–12) cm; heads in subcapitate to loose, spiciform arrays; pappus bristles distinct, falling separately Omalotheca supina
1 Plants 10–70 cm; heads in compact or loose, spiciform arrays; pappus bristles basally connate, falling together > 2
2 Leaf blades: basal and proximal cauline 3-nerved, 6–30 mm wide, distal cauline oblanceolate, faces concolor or weakly bicolor; arrays of heads 1.5–5 cm, rarely interrupted; alpine sites Omalotheca norvegica
2 Leaf blades: basal and proximal cauline 1-nerved, 2–10 mm wide, distal cauline linear, faces bicolor; arrays of heads 4–35 cm, usually interrupted; lower elevations Omalotheca sylvatica