93. Thelesperma Less.

Plants annual or perennial herbs. Stems erect or ascending, unbranched or few- to several-branched, with several fine longitudinal lines or ridges, glabrous or sparsely pubescent with short, more or less spreading hairs at the nodes. Leaves opposite and usually also basal, the uppermost few leaves rarely alternate, short-petiolate to nearly sessile, the petiole sometimes with short, sparse, spreading hairs toward the base, the bases slightly expanded and wrapping around the stem. Leaf blades mostly 1–3 times pinnately dissected, those of the uppermost leaves rarely simple, obovate to fan-shaped in outline (narrowly linear in simple leaves), the ultimate segments narrowly linear (threadlike) or rarely very narrowly oblanceolate, the margins otherwise entire and usually appearing somewhat curled under, glabrous, not glandular. Inflorescences of solitary terminal heads, the heads with long, bractless stalks. Heads radiate or discoid. Involucre cup-shaped to somewhat urn-shaped, the bracts in 2 dissimilar overlapping series. Involucral bracts of the outer series 3–10, shorter than the others, free except sometimes fused at the base, spreading to somewhat ascending, variously shaped, green, usually with thin, pale margins, glabrous, not glandular, inconspicuously 1(3)-nerved; those of the inner series usually 8, fused 1/4–2/3 of the way from the base to the tip, the free portion lanceolate to ovate-triangular, bluish green or yellowish green, membranous to leathery with narrow to broad, lighter, thinner margins, glabrous or minutely fringed at the tip, not glandular, with several to numerous usually conspicuous nerves or longitudinal lines. Receptacle flat or slightly convex, not elongating as the fruits mature, with chaffy bracts subtending the disc florets, these oblong or narrowly ovate, usually somewhat concave and wrapped around the florets, at least toward the base, white or nearly so with usually 2 purplish or reddish nerves. Ray florets absent or present, when present usually 8, sterile (lacking stamens and style at flowering and with an ovary that is shorter and thinner than those of the disc florets, not developing into a fruit), the corolla showy (sometimes inconspicuous elsewhere), 10–22 mm long, relatively broad, yellow, occasionally reddish brown toward the base, not persistent at fruiting. Disc florets 20–100(–120), perfect, the corolla usually 5-lobed, reddish brown or yellow to orangish yellow with reddish brown veins, not thickened at the base, not persistent at fruiting. Style branches with the sterile tip slightly to moderately elongate and tapered to a usually sharply pointed tip. Pappus of the disc florets of usually 2 short awns, these with downward-angled barbs or fine hairs, persistent at fruiting. Fruits 3–8 mm long, sometimes dissimilar in the same head (the shorter, sometimes somewhat curved outer ones grading into the inner ones) narrowly oblong to narrowly oblong-oblanceolate or nearly linear in outline, circular to slightly (and often unevenly) flattened, more or less truncate at the tip, not beaked, the angles lacking wings, the surfaces smooth or 1 or both with irregular wrinkles, ridges, or rounded tubercles (appearing lumpy), otherwise glabrous, brown or black, the black ones somewhat shiny (and usually smooth). About 15 species, U.S., Mexico.

Thelesperma is morphologically similar to some species groups in Coreopsis, differing mainly in the partially united inner series of involucral bracts. Native Americans used species in the genus (mostly T. megapotamicum) medicinally to treat tuberculosis, toothache, and various pediatric ailments. They also derived various dyes from the flowering heads and rootstocks and boiled the young foliage to make a tea (Moerman, 1998).